My two older daughters were the same way when they learned to use the potty, so it's very normal. Sometimes kids refuse out of habit: When they're still in diapers, many toddlers get used to hiding in a corner and squatting to poop; potties are more public, and they can't get into that same squatting position. Some kids just feel anxious about the whole process -- whether it's because moving their bowels takes more effort than peeing, or because they're a bit freaked out by seeing their poop getting flushed away. At 3, they can't always explain themselves.
With some time and patience, he'll be completely diaper-free. Here's what I found helped my daughters along:
- Make sure he has plenty of fiber and water in his diet. If he's constipated, it will only make things worse.
- If he's sitting on the toilet (as opposed to the potty), give him a stool to rest his feet on. It makes it easier to push the poop out.
- Have him sit on the potty/toilet after meals, when he is more likely to poop. He might just go in spite of himself -- and see that it's not so bad!
- Give him lots of kudos for any effort, even if it doesn't produce anything.
- Read kids books about going to the potty, which is a non-threatening way to talk about the subject. Spend some time in the library or bookstore together to find the ones most likely to appeal to him.