Sleep disordered breathing (SDB) is a frequent comorbidity in stroke patients. SDB is one of the independent risk factors for ischemic stroke. Conversely, stroke may contribute to SDB onset or aggravate premorbid SDB. Multiple mechanisms underlying SDB might be responsible for the development of stroke. The aim of this study was to compare polysomnographic, clinical, and laboratory characteristics of wake-up (WUS) and non-wake-up acute ischemic strokes (NWUS). We prospectively enrolled 88 patients with acute ischemic stroke. Clinical characteristics of the population were recorded on admission, and blood samples were obtained in the fasting condition following morning. SDB was assessed using standard overnight polysomnography in the acute phase of the stroke. WUS were present in 16 patients (18.2%), and NWUS in 72 patients (81.8%). In WUS compared to NWUS, we observed significantly higher values of apnea-hypopnea index (24.8 vs. 7.6, p = 0.007), desaturation index ([DI] 26.9 vs. 8.8, p = 0.005), arousal index (22.6 vs. 13.1, p = 0.035), diastolic blood pressure (91.6 mm Hg vs. 85.2 mm Hg, p = 0.039), triglyceride levels ([TG] 1.9 mmol/L vs. 1.2 mmol/L, p = 0.049), and significantly lower levels of D-dimer (0.4 μg/L vs. 0.7 μg/L, p = 0.035). DI (CI: 1.003-1.054, p = 0.031) and TG (CI: 1.002-1.877, p = 0.049) were the only independent variables significantly associated with WUS in binary logistic regression model. Although the design of our study does not prove the causal relationship between SDB and WUS, higher severity of SDB parameters in WUS supports this hypothesis. A commentary on this article appears in this issue on page 467.