OBJECTIVE This study assesses the prevalence of caries and some background factors in 4-year-old children in the city of Umeå, northern Sweden, and compares this with data from earlier studies to reveal changes over time. METHODS Children from the catchment areas of three Public Dental Health Service clinics in Umeå (n = 224) born during the third quarter of 2008 were invited to undergo a clinical dental examination. Decayed surfaces (including both dentine and enamel, except for enamel lesions on buccal and lingual surfaces), missing and filled surfaces (dmfs) were recorded using the same methods and criteria as in a series of earlier studies performed between 1980-2007. Background data were collected in a case-history and a questionnaire. Results. The proportion of children with caries significantly decreased from 2007 (38%) to 2012 (22%) (p < 0.05). In addition, the distribution of dmfs differed significantly between these years (p < 0.05). More immigrant children had caries (42%) than non-immigrant children (15%) (p < 0.05). For children with caries, there were no significant changes in the distribution of dmfs between 1980-2012 (p > 0.05). An immigrant background was associated with a lower frequency of tooth brushing and a higher intake of ice cream, sweets and chocolate drinks (p < 0.05). CONCLUSIONS Although the proportion of children with caries declined between 2007-2012, this decline was limited to non-immigrant children. Since 1980 the distribution of dmfs remained unchanged among children with caries. More research on interventions for changing oral health behaviours is needed, specifically for immigrant children.