It is known that for a nonempty topological space X and a nonsingleton complete lattice Y endowed with the Scott topology, the partially ordered set [X, Y ] of all continuous functions from X into Y is a continuous lattice if and only if both Y and the open set lattice OX are continuous lattices. This result extends to certain classes of Z-distributive lattices, where Z is a subset system replacing the system D of all directed subsets (for which the D-distributive complete lattices are just the continuous ones). In particular, it is shown that if [X, Y ] is a complete lattice then it is supercontinuous (i.e. completely distributive) iff both Y and OX are supercontinuous. Moreover, the Scott topology on Y is the only one making that equivalence true for all spaces X with completely distributive topology. On the way to these results, we find necessary and sufficient conditions for [X, Y ] to be complete, and some new, purely topological characterizations of continuous lattices by continuity conditions on their (infinitary) lattice operations.