Ruth Marks said she had heard of "serious concerns that need to be looked at", including the use of mixed sex wards and the cleanliness of wards.
It is her first review since taking up her post in April 2008.
The former Chief Medical Officer for Wales, Dame Deirdre Hine, will chair the review.
Ms Marks said around 40% of hospital in-patients in Wales were aged 65 or over.
She said: "I want to identify and tackle any standards of care which may exist that are simply unacceptable in 21st Century Wales."
Sarah Stone, deputy commissioner for older people in Wales, said: "In the end it's about making things better for older people.