At present, there is no direct evidence on the relative efficacy in the prevention of restenosis of sirolimus stent and paclitaxel stent after implantation in small coronary vessels. Selecting the most effective device for this particularly high-risk category that accounts for a large proportion of percutaneous coronary interventions, may have important clinical and economic implications. Comparisons of data from subgroup analysis of different trials have suggested that there might be differences in the efficacy to prevent restenosis between sirolimus and paclitaxel stents. However, indirect comparisons are subject to many limitations and consequently, conclusions based on their results may be erroneous. Therefore, reliable guidance on the selection of the most effective drug-eluting stent for treatment of lesions in coronary vessels with a small reference diameter could be provided only from a head-to-head comparison between these devices.