The UEFA Champions League (UCL) is the most important competition at club level. Nevertheless, the sports technical efficiency of this competition has been scarcely analysed. The present paper seeks to fill this gap by analysing from a longitudinal and data panel perspective all the teams that played in the UCL during nine seasons (2004/05 to 2012/13). From a methodological perspective, we have used Data Envelopment Analysis (DEA), a deterministic non-parametric frontier method. In particular, we have applied constant return to scale and variable return to scale DEA assumptions. Due to the tournament characteristics (a group stage in the first phase, and a knockout system in the second phase), we have selected an input-oriented model. As the output (sporting result), we have proposed the use of the coefficients applied by UEFA from UCL revenue distribution. Efficiency is analysed in UCL considering a long period of time and applying the coefficients of revenue distribution as sporting results measurement. On account of differences from previous studies, we are able to obtain some interesting results. First, there is a high inefficiency level in UCL in the analysed seasons. Second, many clubs could be efficient in one season but stop being efficient for all the seasons simultaneously. As a consequence, the teams have many problems maintaining their efficiency during the seasons. Third, we have identified some regular inefficiency sources: waste of resources and inappropriate sporting tactics. Finally, from a longitudinal perspective, it is suggested an improvement in sporting tactics applied by the teams in the last seasons compared with the previous seasons