Match true items from two lists

I have two lists containing only true’s and false’s. For examle: List one: T-T-F-F-T and list two: F-T-T-F-T.
Now I need to find the index where both lists are true, so in this example item 2 and 5. I need to have only the indexes where both are true. I know I can first take out the false’s but then the list index is not representing the original list.
Does somebody know an easy way to solve this?