DD was using a junior pillow at 17 months. she was/is at times a co-sleeper and always wanted to be on my pillow. i had her pillow since she was little but never in her cot just laying around on the floor and when she was around the 17month mark she just picked it up and started laying on it. i think she even pointed to it and tried to say pillow when it was sleep time so i just gave it to her.