The objectives of this study were: to evaluate the change in the three quality of life (QOL) dimensions of vitality, contentment and sleep before intervention and 1 year after treatment with a dental appliance or uvulopalatopharyngoplasty (UPPP); to compare the effect of treatment between these two treatment groups on these three dimensions; and to determine the relation between the QOL scores and somnographic values. Ninety-five patients with mild to moderate obstructive sleep apnoea (OSA) (AI > 5) were randomly allocated to either a dental appliance or UPPP treatment group. Seven patients withdrew after randomization but before treatment, leaving 88 patients eligible for treatment. The patients were examined using somnography and administered the Minor Symptoms Evaluation-Profile (MSE-P), a QOL questionnaire, before and 1 year after intervention. Thirty-seven patients in the dental appliance group and 43 in the UPPP group completed the 1-year follow-up. The mean values for the three dimensions vitality, contentment and sleep improved significantly 1 year after intervention in the dental appliance and UPPP groups. No difference in the QOL scores at baseline was noted between the groups. One year after intervention the UPPP group showed significantly more contentment than the dental appliance group. In contrast, vitality and sleep dimensions did not differ between the two treatment groups. No significant correlations were observed between the QOL scores and somnographic values. In conclusion, quality of life improved significantly in the dental appliance and UPPP groups 1 year after intervention. However, the dental appliance group showed a lower level of contentment than the UPPP group, even though the somnographic values were superior in the former group.