What should we do? My dad has dementia and thinks my mom is alive. He has her pic in her chair and he talks to her and rocks her for hours.

JoAnn's example of what to say is exactly right.

It's a bit late now, but the life-sized picture idea seems to have gone a bit awry - presumably somebody well-meaning gave this to him, he didn't have it printed himself.

I don't think there's any point in trying to remove it as long as he isn't becoming distressed by getting no response. Meanwhile, what about putting together a varied collage of pictures of your mother so that you can talk to him about her and their life together?

I'm very sorry your loss. I hope this reaction of your father's isn't adding too much to everyone else's grief. It must be very hard for you all.

Not much you can do. Depending how far he is into his Dementia telling him she died may end up being a daily thing since short term memory is the first thing to go. And, you shouldn't tell him she died if everytime you do, he grieves all over again. Just play along. "Maybe she is tired Dad and just doesn't feel like talking" "Maybe she isn't hungry now"

Eventually, he may forget Mom. As long as he is content, let him be.