Objective: Sleep problems are a common non-motor complication of Parkinson disease (PD), and patients with essential tremor (ET) share a number of motor and non-motor features of PD. To clarify the relationship between these disorders, we evaluated the sleep problems in patients with ET and PD using assessment scales and objective polysomnographic (PSG) testing. Method: Twenty-one consecutive patients with PD, 16 with ET, and 14 healthy subjects participated in this study and were compared in terms of sleep related complaints, final sleep related diagnosis, and polysomnographic features. Results: The results of our study have shown that patients with PD were more likely than were those with ET to have a history of REM sleep behavior disorders (RBD) (p = 0.001) and excessive daytime sleepiness (p <= 0.05). Additionally, PSG data revealed that ET patients had lower mean SpO(2) values (p <= 0.05) and REM without atonia (RWA) (p = 0.032) than did patients with PD. Conclusion: This is the first study to use PSG to evaluate sleep problems both in ET and PD patients. The results point out different sleep problems in these two common movement disorders which should be investigated in further studies.