Purpose: Cancer patients suffer from a variety of physical and mental complaints. Since physician assessment of symptoms seems insufficient to reveal the complete range of patients’ ailments, patient-reported outcomes (PRO) have become of key importance in modern cancer treatment. The implementation and first results of a systematic electronic real-time assessment of PRO in routine care is described. Methods: Consecutive patients presenting for the first time to a German comprehensive cancer center were asked to fill in an adaptive self-administered electronic questionnaire consisting of standardized PRO measures. After completion, patient-reported data was linked to the patients’ medical files for discussion in the first consultation with the treating physician. Interviews with staff were conducted to identify barriers in implementation. Results: Out of 160 cancer patients, 126 (79 %; mean age 63 years, 67 % males) agreed to participate. The number of recruited patients increased over time. Of participating patients, 67 % provided complete information on all PRO-related scales. On average, 31 min (range 3–140) were required to fill in the questionnaire. Of participating patients, 53.0 % comprised need for psychooncological support and 62 % revealed moderate to severe psychosocial distress. The mean score for global quality of life according to the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30) was 55.2 (SD ±25.6). Conclusions: Comprehensive oncological treatment needs to consider disease symptoms, quality of life, preferences, and comorbidities of individual patients in a structured, standardized, and transparent way. Our findings indicate that an adaptive, self-administered electronic assessment tool for cancer patients to report a broad set of PRO can be feasibly implemented and is well accepted by patients in a realistic setting.