Background: Chronic rhinosinusitis (CRS) is inflammation of the nasal cavity, and paranasal sinuses (PNS) persists for over three months. CRS can be differentiated into CRS with nasal polyps (CRSwNP) or without (CRSsNP). Aim: to determine the allergic cause of sinonasal polyps using the radiological findings of multi-slice Non-contrast computed tomography of the paranasal sinuses (NCCT-PNS) and histopathology results. Materials and Methods: A total of 41 patients with sinonasal polyps were involved in this study. Multislice NCCT-PNS for each patient was taken in coronal sections. Radiological diagnoses were made. Surgical samples were taken after Functional endoscopic sinus surgery (FESS). Histopathological results were collected. Comparison between the NCCT-PNS and histopathology results was made. Statistical analysis was done using the SPSS program. Results: Out of 41 patients involved in this study, 14 males and 27 females. The mean age was 37.4146 ± 16.65. Polyps predominantly were affecting the nose and paranasal sinuses together (p<0.001). Polyps were predominantly bilateral (p<0.001). Sinonasal polyposis was the most commonly diagnosed (58.5%) on CT (p<0.001). Allergic polyps were the most common type of polyps (p=0.003). No significant relationship between gender and allergic or non-allergic causes of polyps (p=0.32, OR= 1.7, 95% CI 0.460-6.280). No significant relationship between gender and specific cause of polyps (p=0.779) except in fungal cause that is more in female. Conclusion: Allergic polyps are the most common type in chronic rhinosinusitis with nasal polyps (CRSwNP). CRSwNP affects female twice as male. Most cases of CRSwNP are bilateral and involve the nose and paranasal sinuses