PURPOSE: This paper was to provide an overview of the research studies on snoezelen with people with developmental disabilities and dementia. METHOD: Computerized and manual searches were carried out to identify the aforementioned studies. Within-session, post-session, and longer-term effects of snoezelen were examined. RESULTS AND CONCLUSION: Twenty-one research studies were identified, 14 concerning people with developmental disabilities and seven people with dementia. Of those studies: 14 reported positive within-session effects; four positive post-session effects; and two positive longer-term effects. These findings were discussed in relation to: (1) methodological aspects (weaknesses) of the studies; (2) the cost of arranging a snoezelen programme and possibilities of reducing the range of stimuli available in the programme; and (3) some research issues for advancing the understanding and effectiveness of intervention programmes with people with developmental disabilities and dementia.