Background: The prevalence of restless legs syndrome (RLS) among the general population is 2–15%, and with fibromyalgia syndrome (FMS) 2%. Both RLS and FMS are more common among women. The aim of our study was to evaluate the prevalence of RLS in a group of female patients diagnosed with FMS and to compare the occurrence of symptoms of daytime sleepiness and experienced sleep disorders between fibromyalgia patients with or without RLS. Method: Three hundred and thirty-two female patients, 20–60 years old, diagnosed with FMS at Skönviks Rehab between 2002 and 2006, answered a questionnaire mailed to their home address. The questionnaire consisted of the international RLS study group criteria as well as of questions concerning symptoms of insomnia and daytime sleepiness measured according to the Epworth Sleepiness Scale. Results: Nearly 64% of the women were also suffering from RLS. More patients suffering from both RLS and FMS were affected by problems of initiating and maintaining sleep than those suffering from FMS only. More patients suffering from both RLS and FMS did not feel refreshed on awakening compared with those suffering from FMS without RLS. The patients with concomitant RLS and FMS were more often hypersomnolent than those suffering from FMS only. Conclusion: This study shows that 64% of a group of female patients diagnosed with fibromyalgia also concurrently suffered from RLS. Compared with patients who suffer from FMS only, patients with both FMS and RLS more often experience sleep disturbances and pronounced daytime sleepiness.