Smith-Magenis syndrome (SMS) is a genetic syndrome most often caused by a deletion on chromosome 17 or more rarely by a mutation in the retinoic acid-induced 1 gene. The aim of this study was to investigate the Developmental Behavior Checklist (DBC) profile of persons with SMS and the associations between behavioural and emotional problems, age, gender, adaptive behaviour and autism symptomatology. Twenty-eight persons with SMS were represented by their parents in this study. DBC Total scores are reduced with age, but they still show a mean that is clearly above the cut-off of 46. The differences between the age groups <9 years and 9-17 years (p = 0.024) and between the age groups <9 years and >18 years (p = 0.007) are significant. We found a significant decrease in behavioural and emotional problems with age in SMS. We did not find a relationship between adapted behaviour and communication and behavioural and emotional problems.