Child abductions by strangers rarely happen in Canada, but exactly how rare is harder to determine.

Police statistics show 25 children of the 46,718 reported missing in 2011 listed as "abducted by stranger."

However, the definition of stranger for these numbers includes anyone who is not a parent. In other words it could be a relative, a friend of the family, a babysitter or someone unknown to the family or victim.

A 2003 study tried to break down those numbers. Marlene Dalley and Jenna Ruscoe, then with the RCMP's National Missing Children Services, studied the 90 stranger abduction missing child reports that had been entered into the national police database in 2000 and 2001. They found just two of those children had been abducted by someone other than a relative or a close family friend.

A search of their own department's Missing Children Registry found an additional three cases. But of those five cases, in the end it turned out that in four of the cases the abductor was known to the family.

According to the report, four of the five children were killed and "it was estimated by the investigating officers that the four victims were killed within the first 24 hours."

In the 2011 statistics, 63 per cent of the missing children and youth reports were over within 24 hours and 86 per cent within a week. In any year the vast majority of the reports turn out to be runaways.

Amanda Pick of the Missing Children Society of Canada says that the rescue of the three abducted young women in Cleveland gives hope to the families of missing children in Canada. (CBC)

Then there are cases where police are still trying to find out what happened to the missing children. That was the case in Cleveland for Michelle Knight, Amanda Berry and Gina deJesus until late Monday afternoon.

"It's not unique to Cleveland, this happens in Canada," Amanda Pick, executive director of the Missing Children Society of Canada (MCSC) told CBC News. Pick explained that for the families she works with, "there are days when you feel hopeless," you think your child is no longer alive.

"Then you will have a day like today, where the unbelievable experience of locating those three women, that gives our families hope that their children are still there," Pick said on Tuesday.

Pick and the MCSC referred CBC News to four of their cases that have been open for years, in which the missing young women were around the age of the three Cleveland women when they were abducted.

Brittany Stalman was 17 when she disappeared in B.C. in 2006. (MCSC)

Brittany Stalman, missing since 2006

Brittany Stalman was 17 when her family reported her missing on Nov. 13, 2006. She left the family home in North Delta, B.C., around 1 p.m., saying she was going for a walk to clear her head after arguing on the phone with her boyfriend.

According to the report by Delta Police, she had left her purse and wallet behind and "Brittany does suffer from bouts of depression." Her mother, Sandra Stalman, said at a 2006 news conference, "You know, she's got ups and downs no different than any other, but she's basically a happy kid."

Delta police said they "have exhausted all traditional avenues but have not yet been able to locate her."

Seven months after Brittany's disappearance, Sandra Stalman told the Vancouver Sun, "She's a very girly girl and liked clothes and nice things and wouldn't want to live on the street."

According to the MCSC, "In the years since their daughter Brittany vanished, her parents have been wandering the trails near their home searching in dread for a trace of their eldest child."

Eva Ho had just turned 17 when she and two friends disappeared in Toronto in 2006. (MCSC )

Eva Ho, missing since 2006

Eight days after her 17th birthday, Yee Wah (Eva) Ho made arrangements with her best friend to meet up at the Eaton Centre in Toronto. Eva didn't show up and hasn't been heard from or seen since, according to Toronto police.

Her boyfriend, Jackie Li, 17, and their mutual friend, Kevin Lim, 18, went missing the same day, Aug. 14, 2006, and they also have not been seen or heard from since.

What makes this case even more extraordinary is that 11 months earlier, a high school friend of the three, Phillip Ho Sing Sit, 17, also went missing and a week before the three went missing, Sit's skeletal remains were found north of Toronto. York Regional Police say Sit was a homicide victim.

In 2007 Toronto police unveiled a life-sized statue of Eva Ho they had commissioned by local sculptor A.D. Milne. They made Ho the subject of their "first Toronto Crime Stoppers YouTube appeal for information" but their efforts have so far been unsuccessful.

Melanie Ethier, then 15, has not been seen or heard from after she went missing in northeast Ontario in 1996. (MCSC )

Melanie Ethier, missing since 1996

In the early hours of Sept. 29, 1996, Melanie Ethier, 15, left a party at a friend's residence in northeast Ontario to walk home, about a kilometre away. She has not been seen or heard from since.

According to the RCMP, "All evidence and data collected to date would indicate that Melanie Ethier has met with foul play at the hands of person(s) unknown."

A Facebook group, Let's Work Together to Find Melanie Ethier, has over 3,000 members. The fate of the New Liskeard teen remains a mystery.

Earlier this month, an art exhibition opened in Sudbury, Ont., with Ethier featured in "The Missing Women Project." The exhibit displays large portraits of 18 missing Ontario women, all painted by Toronto artist Ilene Sova.

Sova says the exhibition, which first opened in Toronto on March 8, is partially aimed at getting people to talk about how police and media treat women's and men's disappearances differently.

It's nearly 20 years since Lindsey Nicholls, 14, went missing in B.C. (RCMP/Canadian Press)

Lindsey Nicholls, missing since 1993

On the morning of Aug. 2, 1993, Lindsey Nicholls, 14, left a group home in B.C.'s Comox Valley to meet up with friends. She never arrived and hasn't been seen since.

In 2011, on Lindsey's 33rd birthday, the RCMP and the MCSC held a press conference on the ongoing investigation into Lindsey's disappearance. After a tip from the public, they conducted a search of a rural property in Royston, near where she was last seen. "The search ended without identifying further information," the MCSC said.

At the press conference, Lindsey's mother, Judy Peterson, said, "My biggest fear is I'll never know what happened to Lindsey."