Cost-effectiveness estimates can help optimize use of available financial resources and this is especially relevant for implementation of cardiac resynchronization therapy (CRT), given the high upfront costs and the timescale of expected benefits. All available cost-effectiveness estimates for devices with (CRT-P) or without (CRT-D) a defibrillator are based on results of randomized trials of selected patients, with a relatively brief follow-up. Extrapolation suggests that the cost effectiveness of CRT may become more favourable as time horizons increase. Using a lifetime time horizon and comparison with optimal medical therapy, the cost effectiveness of both CRT-P and CRT-D appears to meet the $50 000/QALY benchmark commonly used for health-care interventions in the USA, as well as similar thresholds used in Europe. The absence of direct comparisons of the efficacy/effectiveness of CRT-P and CRT-D hampers cost-effectiveness comparisons, and so clinical judgment in the context of current evidence supporting the benefits of cardioverter-defibrillators may provide a rational basis for choosing between CRT-P and CRT-D. Efforts are currently being dedicated to improve CRT response rates by improved patient selection and, reasonably, any improvement in this field will translate into improved effectiveness, and therefore into improved cost effectiveness. The extended longevity of CRT devices will also positively impact cost-effectiveness estimates.