Dogs show considerable variation in morphology, genetics and behaviour caused by long periods of artificial selection. This is evident in the large number of breeds we have today. Behavioural differences among breeds have often been regarded as remnants from past selection during the breeds’ origin. However, the selection in many breeds has, during the last decades, gone through great changes, which could have influenced breed-typical behaviour. In order to investigate this, breed differences were studied using data from a standardized behavioural test from 13,097 dogs of 31 breeds from the Swedish dog population. Based on the test results, breed scores were calculated for four behavioural traits: playfulness, curiosity/fearlessness, sociability and aggressiveness. These traits have previously been found to be stable and valid, and hence regarded as personality traits in the dog. The present results suggested large differences between breeds in all of the investigated traits, even though there were within-breed variations. No relationships between breed-characteristic behaviour and function in the breeds’ origins were found. Instead, there were correlations between breed scores and current use of the breeding stocks, which suggest that selection in the recent past has affected breed-typical behaviour. The breeds’ use in dog shows, the dominating use in general, was negatively correlated with all investigated traits, both in sires and in dams. In contrast, use in Working dog trials was positively correlated with playfulness and aggressiveness in sires. Thus, these results suggest that selection for dog show use is positively correlated with social and non-social fearfulness, and negatively with playfulness, curiosity in potentially threatening situations and aggressiveness, whereas selection for Working dog use is positively correlated with playfulness and aggressiveness. Furthermore, correlation analyses show that popular breeds have higher sociability and playfulness scores than less popular breeds, suggesting that a positive attitude towards strangers is an important characteristic of a functional pet dog and desirable by dog owners. This indicates that selection towards use in dog shows may be in conflict with pet dog selection. Furthermore, these results suggest that basic dimensions of dog behaviour can be changed when selection pressure changes, and that the domestication of the dog still is in progress. A standardized behavioural test, like the one used in this study, is suggested to be highly useful as a tool in dog breeding programs.