Background: With the increase of pediatric cancer survival rates, late effects and quality of life (QoL) have received more attention. Disturbed sleep in pediatric cancer is a common clinical observation, but research on this subject is sparse. In general, sleep problems can lead to significant morbidity and are associated with impaired QoL. Information on sleep is essential to develop interventions to improve QoL.Methods: Children (2-18 years) with acute lymphoblastic leukemia (ALL) were eligible for this multi-center study. The Children's Sleep Habits Questionnaire (CSHQ), Child Health Questionnaire (CHQ) and Pediatric Quality of Life Inventory 3.0™ Acute Cancer Version (PedsQL) were used to assess sleep and QoL halfway through maintenance therapy. Sleep and QoL were measured during and after dexamethasone treatment (on-dex and off-dex).Results: Seventeen children participated (age 6.7 ± 3.3 years, 44% boys). Children with ALL had more sleep problems and a lower QoL compared to the norm. There were no differences on-dex and off-dex. Pain (r = -0.6; p = 0.029) and worry (r = -0.5; p = 0.034) showed a moderate negative association with sleep. Reduced overall QoL was moderately associated with impaired overall sleep (r = -0.6; p = 0.014) and more problems with sleep anxiety (r = -0.8; p = 0.003), sleep onset delay (r = -0.5; p = 0.037), daytime sleepiness (r = -0.5; p = 0.044) and night wakenings (r = -0.6; p = 0.017).Conclusion: QoL is impaired in children during cancer treatment. The results of this study suggest that impaired sleep may be a contributing determinant. Consequently, enhanced counseling and treatment of sleep problems might improve QoL. It is important to conduct more extensive studies to confirm these findings and provide more detailed information on the relationship between sleep and QoL, and on factors affecting sleep in pediatric ALL and in children with cancer in general.