The study was conducted to find out the association of various naso-oro-pharyngeal structures with sleep macro-architecture in suspected obstructive sleep apnea subjects. Study included 51 subjects with suspected obstructive sleep apnea. Subjects with possible central apnea and those consuming any substance that can affect sleep architecture were excluded. Level I polysomnography was performed after thorough physical examination. Overnight study was scored in 30 s epochs to find out the polysomnographic variables. Surgical treatment was offered wherever indicated. Subjects with moderate to severe obstructive sleep apnea were manually titrated on CPAP with the polysomnogram. SPSS v 17.0 was used for statistical analysis. We did not find any difference in the sleep architecture between genders. Sleep Efficiency was better in subjects with dental overjet, dental attrition, high tongue base, macroglossia, lesser oral cavity volume, edematous uvula, increased submental fat, hypertrophied facial muscles and Mallampatti grade III-IV. Shorter Sleep Latency was seen in subjects with tender TMJ and Mallampatti Gr III-IV. REM latency was shorter in subjects with high tongue base, macroglossia and hypertrophied muscles of mastication. Increased REM was observed in subjects with high tongue base, edematous uvula and tender TMJ. Enlarged tonsils had reversed effect with poor sleep efficiency, increased REM latency and decreased REM. CPAP therapy (N = 20) lessened awake time, decreased N2 and increased REM. Oro-pharyngeal structures affect the sleep architecture in suspected OSA subjects. Nasal structures do not affect the sleep architecture in these subjects and enlarged tonsils have opposite effect. Sleep architecture changes on the titration night with CPAP.