mine does too, theyre just playing. just be sure you are well babyproofed, especially all your doors to outside and the bathroom doors, cabinets with chemicals in them, the oven/fridge, etc... this is for her protection as well as your peace of mind so you dont have a complete heart attack when she does it like i did the first few times. then just remember that she is just having fun, and that little kids love to have a little place... let her have a couple of her favorites all to herself, like a little clubhouse, a little tent or a blanket over an end table or something. when she hides in these favorite places, you can play along, she will love it, and teach her the other places are not ok. then she will gravitate to those places where you play along "looking" for her, and you will always know the first place to look. then just keep teaching her that she has to answer you when you call her. i swear i "trained" my first kid just like a dog at that age, i would call him and when he came i gave him a treat, did this over and over and he learned quick. right or wrong, it worked pretty well for a while :)