Communication with children and adolescents with cancer about their disease and treatment and the implications of these is an important aspect of good quality care. It is often poorly performed in practice. Various interventions have been developed that aim to enhance communication involving children or adolescents with cancer. To assess the effects of interventions for improving communication with children and/or adolescents about their cancer, its treatment and their implications, updating the 2003 version of this review. In April 2006 we updated searches of the following sources: CENTRAL (The Cochrane Library, issue 1 2006); MEDLINE (Ovid), (2003 to March week 5 2006); EMBASE (Ovid) (2003 to 2006 week 13); PsycINFO (Ovid) (2003 to March week 5 2006); CINAHL (Ovid) (2003 to March week 5 2006); ERIC (CSA) (earliest to 2006); Sociological Abstracts (CSA) (earliest to 2006); Dissertation Abstracts: (2002 to 6 April 2006).In 2003 we conducted searches of CENTRAL; MEDLINE, EMBASE, PsycINFO, CINAHL, ERIC, Sociological Abstracts and Dissertation Abstracts.For the initial (2001) publication of this review we also searched the following databases: PsycLIT; Cancerlit; Sociofile; Health Management Information Consortium; ASSIA; LISA; PAIS; Information Science Abstracts; JICST; Pascal; Linguistics and Language Behavior Abstracts; Mental Health Abstracts; AMED; MANTIS.We also searched the bibliographies of studies assessed for inclusion, and contacted experts in the field. Randomised and non-randomised controlled trials, and before and after studies, evaluating the effects of interventions for improving communication with children and/or adolescents about their cancer, treatment and related issues. Data relating to the interventions, populations and outcomes studied and the design and methodological quality of included studies were extracted by one review author and checked by another review author. We present a narrative summary of the results. One new study met the criteria for inclusion; in total we have included ten studies involving 438 participants. Studies were diverse in terms of the interventions evaluated, study designs used, types of people who participated and the outcomes measured.One study of a computer-assisted education programme reported improvements in knowledge and understanding about blood counts and cancer symptoms. One study of a CD-ROM about leukaemia reported an improvement in children's feelings of control over their health. One study of art therapy as support for children during painful procedures reported an increase in positive, collaborative behaviour. Two out of two studies of school reintegration programs reported improvements in some aspects of psychosocial wellbeing (one in anxiety and one in depression), social wellbeing (two in social competence and one in social support) and behavioural problems; and one reported improvements in physical competence. One newly-identified study of a multifaceted interactive intervention reported a reduction in distress (as measured by heart rate) related to radiation therapy.Two studies of group therapy, one of planned play and story telling, and one of a self-care coping intervention, found no significant effects on the psychological or clinical outcomes measured. Interventions to enhance communication involving children and adolescents with cancer have not been widely or rigorously assessed. The weak evidence that exists suggests that some children and adolescents with cancer may derive some benefit from specific information-giving programs, from support before and during particular procedures, and from interventions that aim to facilitate their reintegration into school and social activities. More research is needed to investigate the effects of these and other related interventions.