  The aim of this paper is to prove the existence and uniqueness of solutions
of the following $q$- Cauchy problem of second order linear $q$-difference
problem associated with the Rubin's $q$- difference operator $\partial_q$ in a
neighborhood of zero \begin{equation} \left\{ \begin{array}{cc} q\,a_0(x)\,
\partial_q^2y(qx)\, +\ ,a_1(x)\,\partial_qy(x)\, + \,a_2(x)y(x) &\; =
\;b(x),\quad \hbox{if $y$ is odd;}\\ q\,a_0(x) \partial_q^2y(qx)\, +
\,q\,a_1(x)\partial_qy(qx)\, + \,a_2(x)y(x)&\; = \;b(x),\quad \hbox{if $y$ is
even,} \end{array} \right. \end{equation} with the initial conditions
\begin{equation} \partial_{q}^{i-1}y(0)= b_{i};\quad b_{i} \in{\mathbb{C}},\;
i=1,2 \end{equation} where $a_i$, $i=0,1,2$, and $b$ are defined, continuous at
zero and bounded on an interval $I$ containing zero such that $a_0(x)\neq 0$
for all $x\in I$. Then, as application of the main results, we study the second
order homogenous linear $q$- difference equations as well as the $q$-Wronskian
associated with the Rubin's $q$-difference operator $\partial_q$. Finally, we
construct a fundamental set of solutions for the second order linear
homogeneous $q$-difference equations in the cases when the coefficients are
constants and $a_1(x)=0$ for all $x\in I$.
