When is it safe to introduce a pillow?

Hi,
I have an 18mth old and she still sleeps in a cot. I was just wondering when is it ok to use a pillow? If I do it will be a very slim pillow. Or should I just wait until she is in a bed like I did with the oldest?

I think pillows are best left until they old enough for a bed.

Cheers Maree

I gave mine pillows when they went into a bed, but they were in beds by 12 months.