  This paper is divided in two parts. In the first part we consider irregular
singular analytic q-difference equations, with q\in ]0,1[, and we show how the
Borel sum of a divergent solution of a differential equation can be uniformly
approximated on a convenient sector by a meromorphic solution of such a
q-difference equation. In the second part, we work under the assumption q\in
]1,+\infty[. In this case, at least four different q-Borel sums of a divergent
solution of an irregular singular analytic q-difference equations are spread in
the literature: under convenient assumptions we clarify the relations among
them.
