Q:

Asteroids between Mars and Jupiter

Is the cluster of asteroids between Mars and Jupiter two dimensional as seen in every model of solar system shown in books or television? Or is it three dimensional as i think it should be?

A:

Many models shown in books or television show a very populated asteroid belt but in fact the belt is mostly empty. 
To answer your question, the inclination of the asteroids vary a lot going from 0° to 40° although most off them are in between 0° and 30°; See The orbital element distributions of real and modelled asteroids. So yes it would be 3 dimensional.

