Investors looking to make some money are likely to take the traditional route and bet on stocks and bonds. But what about that stash of old comic books lying around in the attic? They have the potential to be more lucrative than you may think.

Anders Nilsson from Gocompare.com told Yahoo Finance’s Alexis Christoforous in the video above that comic books can spell a big payday for investors.

“We found that a significant proportion of the highest value comics have been outperforming more traditional investments like the S&P 500 (^GSPC) or even gold (GCM16.CMX),” said Nilsson.

Gocompare.com collected information on comic books to determine those that have appreciated the most in price since 2008 compared to the S&P 500’s performance. The top performer was DC's Batman Adventures #12, first published in 1993. The original cost of the issue was $1.25, and in the last eight years, it has appreciated in price to $800, making a 26,567% return.

“We saw it really take off in terms of rising in value on news that a Suicide Squad spin-off might be in the cards. Then it really rocketed when the producer signed up in 2014, and it was confirmed. That particular comic features Harley Quinn, who we know is going to be one of the main characters in Suicide Squad,” said Nilsson. Suicide Squad will be released in August.

The second best performer was Marvel’s New Mutants, which appreciated 4,900% in value since 2008. The price of the comic when first published was $1.00. It now sells for $250. Similar to DC’s Batman Adventure #12, New Mutants saw its value surge on hype surrounding the movie Deadpool, which was released in February.

In terms of value, the comic taking the number one spot is Action Comics #1, the edition in which readers meet Superman and Lois Lane for the very first time. The price of the comic when first published in 1938 was $0.10. Now it’s worth a staggering $3 million.

But if you’re thinking about investing in comics, it’s important to note that there's a pretty small window for success. Therefore, it’s important for potential buyers to know what to look for.

“Look for rare first editions where characters are being introduced for the first time,” said Nilsson. “Try to look for characters that are going to be featured in films… A big thing to look out for is keeping its relevance by being on the big screen.“