The present invention relates to a system (10), method and terminal (14) for measuring the quality of service or QoS for services, for example, of the Internet type in which a telecommunications network (12) supports the delivery of the services by a server (16). The system (10) and the corresponding method allow to collect by means of the network (12, 18, 20) the QoS information, in particular information of insufficient QoS, to identify the causes of insufficient QoS and to discriminate in the attribution of said causes among the terminal (14), the server (16) or the network itself (12). The terminal (14) in addition to generating "objective" information about the QoS, such as the time for downloading a Web page, dimensions of the Web page and number of objects composing the page, is also able to generate "subjective" information, indicative of the actual QoS perceived by a user of the terminal (14).