Acute lymphoblastic leukaemia (ALL) is the most common form of paediatric leukaemia. The survival rate in children with ALL has improved significantly over the past several years, which makes quality of life an important focus for researchers. Some of the side effects of treatment (i.e. osteoporosis and obesity) are not realized until years after conclusion of therapy. Few studies have addressed the impact of physical activity (PA) on the side effects that occur during treatment of children with ALL. This paper discusses the increased risk for both osteoporosis and obesity due to treatment for ALL and suggests ways that PA may attenuate bone loss and risk of obesity by discussing what is known about effects of PA in healthy children and children with other chronic diseases. Recommendations will be made for PA interventions and future research in children with ALL.