Abstract International projects such as the Joint Action on strengthening eHealth including telemedicine and remote monitoring for health care systems for cancer prevention and care (eCAN) are implemented in countries with different languages, requiring validation of translations of standardized tools. Evaluation frameworks for telemedicine services necessarily include the patient’s perspective, i.a. on the service usability. Due to the lack of validated questionnaires in multiple European languages we sought to develop translation for the languages of the eCAN pilot countries. Based on literature review, we selected mHealth App Usability Questionnaire (MAUQ) and Telehealth Usability Questionnaire (TUQ) and developed a conceptual definition for each item. Next, we performed forward and back translation from English into the target languages, expert review, cognitive interview (CI) with 5-10 cancer or chronic disease patients per language/per questionnaire. Qualitative CI results were scored by 2 independent researchers for consistence of each item with conceptual definitions for final review by native speaker expert. We chose 8 languages (ES, GR, HU, IT, LT, NL, PT, SI) for validation. CI involved 48 respondents (29 females, 60%; 18 aged>60, 38%;23 higher education, 48%) for TUQ and 48 (22 females, 46%; 16 aged>60, 33%; 23 higher education, 48%) for MAUQ. Overall 872 (87%) of TUQ and 728 (84%) of MAUQ item answers were classified as consistent. In more than one language we identified concepts difficult to understand: consistent navigation when moving between screens, distinction between easy to use/learn, social settings. The validation process allowed us to identify opportunities to improve translation and highlighted concepts generally more difficult to understand. We provided validated translation of MAUQ and TUQ in 8 European languages for use in eCAN pilots and future telemedicine evaluation studies. Key messages • eCAN successfully validated translations of telemedicine usability questionnaires for 8 languages. • Multilingual translation validation can provide insights into concepts difficult across languages.