This study was done to evaluate the frontal sinus dimensions in skeletal Class I and Class II malocclusions and its relationship to craniofacial dimensions which includes the anterior and posterior cranial base lengths, maxillary length and the mandibular length. METHODOLOGY: This study was conducted using the lateral cephalograms procured from the orthodontic records submitted in the department of orthodontics at the School of Dental Sciences, Sharda University. A total of 120 lateral cephalograms were obtained from the orthodontic records submitted in the department of orthodontics at the School of Dental Sciences, Sharda University, which comprised of male and female patients with skeletal class I and Class II malocclusion. CONCLUSION: Frontal sinus dimensions in males are larger as compared to females in both Class I and Class II malocclusion but the ratio of frontal sinus height to widthremained same in both males and females. Frontal sinus height to width ratio was found to be different in both Class I and Class II malocclusions in males as well as females. In males, frontal sinus ratio in patients having Class II malocclusion was greater than Class I malocclusion. Frontal sinus width was smaller in Class II but frontal sinus height remained the same in both the groups.