Obstructive Sleep Apnea and Obesity Hypoventilation Syndrome are two similar diseases. Obstructive Sleep Apnea has been receiving more and more attention while the diagnostic rate of Obesity Hypoventilation Syndrome is not high. Few studies directly evaluated the relationship between them. We systematically analyzed the relevance of the two diseases. MEDLINE (R), EMBASE (R) and the Cochrane Library were carried out to find studies until May 2017. Pooled mean difference and 95% confidence interval were calculated to evaluate the value of clinical and physiologic variables in the prediction of Obesity Hypoventilation Syndrome. 9 Studies (n = 2085) fulfilled the predefined selection criteria. Totally 575 patients (28%) with Obesity Hypoventilation Syndrome were diagnosed from 2085 Obstructive Sleep Apnea patients. Among clearly diagnosed Obstructive Sleep Apnea patients, higher Body Mass Index levels(mean difference: 4.72 kg/m(2); 95% confidence interval: 4.26 to 5.17; p < 0.00001), higher Apnea-Hypopnea Index (mean difference: 8.36; 95% confidence interval: -3.88 to -2.84; p < 0.00001), greater neck circumference (mean difference: 1.01; 95% confidence interval: 0.10 to 1.92; p = 0.03) and lower percent predicted FEV1 (mean difference:-10.28; 95% confidence interval:-11.33 to -9.22; p < 0.00001) were associated with the occurrence with obesity hypoventilation syndrome. We should be highly skeptical of obesity hypoventilation syndrome in Obstructive Sleep Apnea patients with these factors as early identification and appropriate treatment can improve prognosis.