Double health insurance coverage exists when an individual benefits from more than one health insurance plan at the same time. We examine the impact of such supplementary insurance on the utilisation of doctor consultations in Portugal, taking advantage of institutional features which make double coverage plausibly exogenous. The novelty is that the analysis is carried out for different points of the conditional distribution, not only for its mean location, within the context of count data modelling and without imposing restrictive parametric assumptions. Results indicate that double coverage creates additional utilisation of health care across the whole outcome distribution for both public and private second layers of health insurance coverage but with greater magnitude in the latter group. We unveil that this additional consumption effect is relatively smaller for more frequent users. Copyright (C) 2010 John Wiley & Sons, Ltd.