Background The utility of inpatient vs outpatient polysomnography (PSG) for individuals with sleep-disordered breathing is unclear. Research Question How do patient characteristics and sleep medicine care patterns differ between individuals undergoing inpatient vs outpatient PSG? Study Design and Methods We conducted a retrospective population-based health administrative database study on all adult Ontarians (Canada) hospitalized and/or who underwent PSG between 2012 and 2018. We compared individuals who underwent PSG: (1) during hospitalization (inpatient PSG), (2) within the first month after discharge (delayed PSG), and (3) were not hospitalized in the last year (outpatient PSG). Outcomes included the following: baseline characteristics at the time of PSG, outpatient follow-up rates, and positive airway pressure claims in the year after PSG. Results We identified 748 individuals in the inpatient group, 9,310 in the delayed group, and 730,967 in the outpatient PSG group. Compared with delayed or outpatient PSG groups, in unadjusted analyses, individuals in the inpatient PSG group were more likely to be older, previously assessed for sleep-disordered breathing, reside in a low-income neighborhood, and have greater comorbidity burden (standardized differences > 0.10). In adjusted analysis, individuals in the inpatient PSG group were less likely to be seen in the sleep clinic within the first year after PSG than the delayed or outpatient PSG group (hazard ratio [HR], 0.79; 95% CI, 0.71-0.87), with no difference between the delayed and outpatient PSG groups (HR, 1.00; 95% CI, 0.98-1.03). Compared with the delayed or outpatient PSG group, those in the inpatient PSG group were 21% (HR vs delayed group, 0.79; 95% CI, 0.67-0.94) to 53% (HR vs outpatient group, 0.47; 95% CI 0.27-0.82) less likely to initiate CPAP or auto-titrating positive airway pressure, and 2 to 10 times more likely to initiate bilevel positive airway pressure (HR vs outpatient group, 10.03; 95% CI, 7.30-13.77). Interpretation Our results indicate that individuals undergoing inpatient PSG represent a unique smaller subgroup with greater comorbidity and social disadvantage, whereas the delayed PSG group may represent an optimal model of care, informing directions for future prospective studies.