Background e-Learning is an underutilized tool in education for the health professions, and radiation medicine, given its reliance on technology for clinical practice, is well-suited to training simulation in online environments. The purpose of the present study was to evaluate the knowledge impact and user interface satisfaction of high- (hf) compared with low-fidelity (lf) e-learning modules (e-modules) in radiation oncology training.Methods Two versions of an e-module on lung radiotherapy (lf and hf) were developed. Radiation oncology residents and fellows were invited to be randomized to complete either the lf or the hf module through individual online accounts over a 2-week period. A 25-item multiple-choice knowledge assessment was administered before and after module completion, and user interface satisfaction was measured using the Questionnaire for User Interaction Satisfaction (quis) tool.Results Of 18 trainees, 8 were randomized to the lf module, and 10, to the hf module. Overall, knowledge assessment performance increased (11%, p < 0.05), with hf-group participants reporting a 13% improvement (p = 0.02), and senior participants reporting an almost 15% improvement (p < 0.01). Scores on the quis indicated that participants were satisfied with various aspects of the user interface.Conclusions The hf e-module had a greater impact on knowledge acquisition, and users expressed satisfaction with the interface in both the hf and lf situations. The use of e-learning in a competency-based curriculum could have educational advantages; participants expressed benefits and drawbacks. Preferences for e-learning integration in education for the health professions should be explored further.