– Four patients, a woman aged 60 and three men aged 61, 53 and 56 years, presented with hypersomnia during the day. The cause was determined by polygraphic registration and was a variable combination of sleep apnoea syndrome, narcolepsia and periodic movements of the limbs in sleep syndrome (PMLS). Such a combination may lead to a therapeutic paradox as the treatment of one disturbance may lead to aggravation of another one. Therapy is possible but only when it is completely clear which component of the disorder prevails. Whole night polygraphy is indispensable for this approach.