Why do you need the smallest smart phone? Imagine having to travel. Space would be a commodity in this case. Travelling light is going to help you manage your stuff better and to minimise lost of baggage so if you have a small smartphone, you can just toss it in to your pocket or hand carry it easily.
However, which are the smallest smartphones in the market? Most smartphones have similar sizes, although some can be big while others can be small. The smallest to be introduced into the market is the Mini Nokia N97 handset available from Mobile Phone Deal