To assess the accuracy of a wrist worn Watch PAT 200 in diagnosing obstructive sleep apnea hypopnea syndrome (OSAHS) by comparing with the standard polysomnography (PSG).Twenty-eight adults with suspected OSAHS underwent a standard in-lab PSG while wearing a Watch PAT 200. PSG events were manually scored according to standard criteria (AASM). Watch PAT data were collected including changes of apnea hypopnea, sleep stages, peripheral arterial volume, signal oxygen saturation and heart rate, and then apnea hypopnea index (AHI) was analyzed by an automatic algorithm.For PSG, the mean score of AHI was (23.00 +/- 21.55)/h, and for Watch PAT, a mean score of AHI was (25.99 +/- 19.09)/h. There is a statistically positive correlation between PSG-AHI and PAT-AHI (r = 0.92, P < 0.01). The Coincidence rate of the sleep-wake assessment based on 30-second bins between the PSG and Watch PAT 200 was (89 +/- 6)%.Watch PAT 200 could detected OSAHS based on AHI with comparable accuracy with standard PSG. And it would provide a reasonably accurate estimation of sleep and wakefulness stages in patients with OSAHS.