Background Long-term physical conditions aC ect 10% to 12% of children and adolescents worldwide. These individuals are at greaterrisk of developing psychological problems, particularly anxiety and depression, sometimes directly related to their illness or medical care (e.g. healthrelated anxiety). There is limited evidence regarding the eC ectiveness of psychologicaltherapies fortreating anxiety and depression in this population. Therapies designed for children and adolescents without medical issues may or may not be appropriate for use with those who have long-term physical conditions. Objectives This review was undertaken to assess the eC ectiveness and acceptability of psychological therapies in comparison with controls (treatment-as-usual, waiting list, attention placebo, psychological placebo, or non-psychological treatment) for treating anxiety and depression in children and adolescents with long-term physical conditions. Search methods We searched Ovid MEDLINE (1950- ), Embase (1974- ), PsycINFO (1967- ) and the Cochrane Central Register of Controlled Trials (CENTRAL) to 27 September 2018. An earlier search of these databases was conducted via the Cochrane Common Mental Disorders Controlled Trial Register(CCMD-CTR)(all years toMay 2016). In addition, we searched theWeb of Science (Core Collection)(12October 2018) and conducted a cited reference search for reports of all included trials. We handsearched relevant conference proceedings, reference lists of included articles, and grey literature. Selection criteria Randomised controlled trials (RCTs), cluster-randomised trials and cross-over trials of psychological therapies for treating anxiety or depression in children with long-term physical conditions were included. Data collection and analysis Abstracts and complete articles were independently reviewed by two authors. Discrepancies were addressed by a third author. Odds ratio (OR) was used for comparing dichotomous data and standardised mean diC erences (SMD) for comparing continuous data. Meta-analysis was undertaken when treatments, participants, and the underlying clinical question were similar. Otherwise, narrative analysis of data was undertaken Main results Twenty-eight RCTs and one cross-over trial with 1349 participants were included in the review. Most participants were recruited from community settings and hospital clinics in high-income countries. For the primary outcome of treatment eC icacy, short-term depression (versus any control), there was low-quality evidence from 16 trials involving 1121 participants suggesting that psychological therapies may be more eC ective than control therapies (SMD -0.31, 95% CI -0.59 to -0.03; I 2 = 79%). For the primary outcome of treatment eC icacy, short-term anxiety (versus any control), there was inadequate evidence of moderate-quality from 13 studies involving 578 participants to determine whether psychological therapies were more eC ective than control conditions (SMD -0.26, CI -0.59 to 0.07, I 2 = 72%). Planned sensitivity analyses could not be undertaken for risk of bias due to the small number of trials that rated high for each domain. Additional sensitivity analysis demonstrated that psychological interventions specifically designed to reduce anxiety or depression were more eC ective than psychologicaltherapies designed to improve other symptoms or general coping. There was some suggestion from subgroup analyses thatthey type of intervention (Chi2 = 14.75, df = 5 (P = 0.01), I2 = 66.1%),the severity of depression (Chi2 = 23.29, df = 4 (P = 0.0001), I2 = 82.8%) and the type of long-term physical condition (Chi2 = 10.55, df = 4 (P = 0.03), I2 = 62.1%) may have an impact on the overalltreatment eC ect.There was qualitative (reported), but not quantitative evidence confirming the acceptability of selected psychological therapies for anxiety and depression. There was low-quality evidence that psychological therapies were more eC ective than control conditions in improving quality of life (SMD 1.13, CI 0.44 to 1.82, I 2 = 89%) and symptoms of long-term physical conditions (SMD -0.34, CI -0.6 to -0.06, I 2 = 70%), but only in the short term. There was inadequate low-quality evidence to determine whether psychological therapies were more eC ective than control conditions atimproving functioning in eitherthe shortterm orlong term.No trials oftherapies for addressing healthrelated anxiety were identified and only two trials reported adverse eC ects; these were unrelated to psychological therapies. Overall, the evidence was of low to moderate quality, results were heterogeneous, and only one trial had an available protocol. Authors' conclusions A limited number of trials of variable quality have been undertaken to assess whether psychological therapies are eC ective for treating anxiety and depression in children and adolescents with long-term physical conditions. According to the available evidence, therapies specifically designed to treat anxiety or depression (especially those based on principles of cognitive behaviour therapy (CBT)) may be more likely to work in children and adolescents who have mild to moderate levels of symptoms of these disorders, at least in the short term. There is a dearth of therapies specifically designed to treat health-related anxiety in this age group