The aim of this review was to evaluate the scientific evidence for an effect of psychosocial intervention on survival from cancer and well-being and in particular on anxiety and depression. A literature search yielded 43 randomised studies of psychosocial intervention. Four of the eight studies in which survival was assessed showed a significant effect, and the effect on anxiety and depression was also inconsistent, indicating three possible explanations: (i) only some of the intervention strategies affect prognosis and/or well-being and in only certain patient groups; (ii) the effect was weak, so that inconsistent results were found in the generally small study populations; or (iii) the effect was diluted by the inclusion of unselected patient groups rather than being restricted to patients in need of psychosocial support. Thus, large-scale studies with sound methods are needed in which eligible patients are screened for distress. Meanwhile, the question of whether psychosocial intervention among cancer patients has a beneficial effect remains unresolved.