There is still little research on psychological wellbeing and reported problems in preadolescents and adolescents under therapy for leukemia, also comparing them with their healthy peers. The present study aims to analyze the life perceptions, psychological well-being and problems’ intensity in these patients during the first year of therapy and to compare these reports with those of matched healthy peers adopting a battery of self-report questionnaires. Mann-Whitney tests identified the younger patients more at risk than older ones in their problems’ intensity and psychological symptoms. Older patients resulted instead more vulnerable regarding past life perceptions. Wilcoxon test with 2 dependent samples analyses showed that: healthy peers have a better perception of current life and lower percentage of somatization symptoms than patients after 6-months post-diagnosis. On the other hand, healthy peers reported more problems dealing with impulsivity, mood, disorganization, concentration and memory than patients both at 6-months and 1-year from diagnosis. Healthy peers reported also more anxiety and depression symptoms than patients and worse past and future life perceptions than patients at 1-year from diagnosis. The clinical aim is to perform a psychological screening of preadolescents and adolescents in order to prepare ad hoc psychological interventions.