This paper presents a questionnaire-based approach to evaluate the user experience (UX) while interacting with interactive Television (iTV) systems. Current contributions in the field of UX propose generic methods applicable to various application domains, whereas our contribution is dedicated to the specific domain of interactive TV systems. Based on a classification of UX dimensions from a literature review, the first version of the questionnaire is focusing on the dimension's aesthetics, emotion, stimulation and identification. A validation study with 106 participants was performed to assess the relations between the evaluated UX dimensions, as well as their fit to the underlying theoretical assumptions. Results showed that the UX dimensions aesthetics, emotion and stimulation are important for the domain of iTV, while identification was not confirmed. The study revealed significant correlations between the type of IPTV system used and the emotional and stimulation dimension. Additionally, a significant effect of the TV reception mode and the type of IPTV box owned on the emotion towards the system was observed. Beyond the contribution of the questionnaire that is directly applicable for any iTV system, the findings described in the paper demonstrate the need for user experience evaluation methods targeted at specific domains: the validation of the questionnaire shows that identification is not a central dimension of user experience when interacting with interactive TV.