  We consider a nonlinear Dirichlet problem driven by the $(p,q)$-Laplacian and
with a reaction which is parametric and exhibits the combined effects of a
singular term and of a superdiffusive one. We prove an existence and
nonexistence result for positive solutions depending on the value of the
parameter $\lambda \in \overset{\circ}{\mathbb{R}}_+=(0,+\infty)$.
