MijnAVL” is an interactive portal for cancer patients that includes patient education, an overview of appointments, access to the electronic medical record, patient-reported outcomes and related feedback, and tailored physical activity support. The aim of this study was to evaluate MijnAVL’s feasibility and preliminary efficacy among lung cancer patients. Methods: We included individuals currently or recently treated for lung cancer with curative intent (surgery or radiotherapy). At baseline, they completed a questionnaire on sociodemographics, expectations of MijnAVL and three effect measures: patient activation (PAM), quality of life (SF-36), and physical activity (IPAQ). MijnAVL could be used noncommittally for 4 months. After this period, log data were collected retrospectively and participants completed questions on satisfaction and the effect measures. Results: We included 37 patients (mean age 59.6 years). The mean number of logins was 11.2 with a mean duration of 12.9 minutes. Eighty-nine percent of patients indicated that MijnAVL was easy to use and 82% was positive about using it. Many patients (69%) indicated that MijnAVL was a valuable addition to the care they received and 56% indicated that it helped them to have more control over their health. All features were frequently used and rated 7 or higher on a 10 point scale. Website user satisfaction was rated, on average, 3.9 on a 5 point scale. Patient activation decreased over time from 64.8 to 59.4 (p= 0.049), meaning patients felt less activated. For the SF-36, we found no significant changes over time. In general, levels of physical activity did not change, although vigorous physical activity tended to increase over time (from median of 0 to 360 MET-minutes per week (p= .053)). Conclusions: These results indicate that using MijnAVL is feasible in lung cancer patients. Most users indicated that MijnAVL was useful and easy to use. The efficacy of the patient portal could not be substantiated, which could be due to small sample size, the intervention itself, the (insensitivity of) outcome measures, or a combination of these. Further research is needed to find effective ways to improve and adequately measure patient empowerment in lung cancer survivors.