In this paper we present a usability measure adapted to mobile services, which is based on the well-known theoretical framework defined in the ISO 9241-11 standard. This measure is then applied to a representative set of services of the Telefónica’s portfolio for residential customers. The user tests that we present were carried out by a total of 327 people. Additionally, we describe the detailed application of the methodology to a particular service and present the results of all the experiments that were carried out with the different services. These results show highly significant differences in the three usability measures considered (effectiveness, efficiency and satisfaction), though all of them have the same trend. The worst performers in all cases were the WAP and i-mode user interfaces (UI), while the best performers were the SMS and web based UIs closely followed by the voice UI. Finally, we also analyse the results and present our conclusions.