A fairly detailed survey on the q-classical orthogonal polynomials of the Hahn class and the extensions of the classical polynomials on non-uniform lattices is presented. Such polynomials appear to be the bounded solutions of the corresponding difference equations of hypergeometric type. The central idea behind this book is to discuss the orthogonality of all possible polynomial solutions of the q-hypergeometric difference equation by means of a qualitative analysis of the relevant q-Pearson equation, moreover, a general theory of the Krall-type polynomials on q-quadratic lattices