We have used multi-band high resolution HST WFPC2 and ACS observations combined with wide field ground-based observations to study the blue straggler star (BSS) population in the galactic globular cluster NGC 6388. As in several other clusters we have studied, the BSS distribution is found to be bimodal: highly peaked in the cluster center, rapidly decreasing at intermediate radii, and rising again at larger radii. In other clusters the sparsely populated intermediate region (or ``zone of avoidance'') corresponds well to that part of the cluster where dynamical friction would have caused the BSS or their binary progenitors to sunk to the cluster center. Instead, in NGC 6388, BSS still populate a region that have been cleaned out by dynamical friction effects, thus suggesting that dynamical friction is somehow less efficient than expected.