Cancer-related fatigue is one of the most frequently reported symptoms after treatment for (non-)Hodgkin lymphoma. This dissertation describes the procedure and results of the SPARKLE trial which primarily aimed to investigate whether light therapy can be used as a treatment for chronic cancer-related fatigue since the diagnosis of Hodgkin lymphoma or diffuse large B-cell lymphoma. Secondary aims included the investigating of the effect of light therapy on symptoms related to cancer-related fatigue, for example depression, anxiety, quality of life, sleep quality, cognitive complaints and cognitive functioning. Objective measurements of the sleep-wake cycle (assessed with actigraphy) and circadian rhythms (melatonin and cortisol from saliva) were also included. An additional chapter describes the psychometric evaluation of the Multidimensional Fatigue Inventory. This questionnaire was one of the primary outcomes of the SPARKLE trial. The final chapter describes a critical evaluation of the results of the SPARKLE trial compared to the current literature, offers clinical implications and proposals for future research.