Background: Chronic rhinosinusitis (CRS) is a major disease condition with high morbidity and can influence lower airway disease status in adults. However, its associations with adult asthma onset and activity have not been examined in detail in a general adult population. Objective: To investigate relationships between CRS with nasal polyps (CRSwNP) and asthma characteristics. Methods: A cross-sectional data set of 17,506 adult participants (≥18 years old) in the Korean National Health and Nutrition Examination Survey from 2010 through 2012 was analyzed. CRS was defined using structured questionnaires according to the international guideline, and presence of nasal polyps was objectively assessed using nasal endoscopy. Presence of asthma and its onset and current activity were assessed using structured questionnaires. Results: CRS was significantly related to asthma, but the relationships were distinct by CRS and asthma status. CRSwNP was significantly associated with adult-onset asthma (onset after 18 years of age) or late-onset asthma (onset after 40 years of age), whereas CRS without nasal polyps was related to childhood-onset asthma (onset before 18 years) or early-onset asthma (onset before 40 years) in adults. The 2 CRS subgroups showed significant associations with current asthma but not with past asthma. However, the comorbid asthma rate was lower than 10% among subjects with CRS. Conclusion: This study found distinct age-related patterns of CRSwNP and asthma and demonstrated their significant associations in a general population. However, the low prevalence of asthma in CRSwNP is in sharp contrast to findings in Western populations, which warrants further investigation for ethnic or regional differences in relationships between CRSwNP and asthma.