User satisfaction is one of the key characteristics of software products including the web-sites’ quality. An absence of generally accepted instruments for evaluation of the user satisfaction creates a significant impediment for empirical studies on usability of software products. In the paper there are discussed the results of elaboration of a new psychodiagnostic tool that can be used for these purposes. It is presented in the form of a standardized questionnaire with well-balanced content, high internal consistency and differential sensitivity. The instrument provides a multidimensional evaluation of user satisfaction as a way for ergonomic redesign of a web-site interface.