The costumes have been chosen and fundraising tins are prepped for the 23rd annual Radio Lollipop Uniform Free Day on Wednesday.

Transperth bus and train drivers and other PTA staff will once again hang up their uniforms and don fun costumes to raise money for sick kids in WA hospitals.

Transperth drivers will don fancy dress for this week's fundraiser.

Radio Lollipop, which stands for Lots Of Love and Laughter In Place Of Pain, is a children's charity which sets out to bring a little ray of sunshine to children in hospital, with in-ward activities and visits from volunteers, as well as a nightly kids radio show which they can call in to from their beds and request their favourite songs.

PTA managing director Mark Burgess said more than $77,000 was raised by staff and passengers during last year's Radio Lollipop Uniform Free Day.