Correction of cleft lip nasal deformity is an elusive goal. Controversy exists regarding the cause of the deformity and therefore there is a controversy of how to correct the deformity. Extrinsic theory is based on the presence of deformational forces from outside. The intrinsic theory is associated with deficiency of the lower lateral cartilage. The aim of this study is to compare morphologically and histologically between the lower lateral cartilages of cleft and non cleft sides in patients with unilateral cleft lip nasal deformity. This study included 16 patients (5-22 years old). They were operated upon to correct unilateral cleft lip nasal deformity. Length, width and thickness of lateral crura of lower lateral cartilages of cleft and non cleft sides were measured. Punch biopsies from the middle part of the caudal ends of lateral crura were taken and sent for histological and immune histochemical studies. The lateral crus of the cleft side, was significantly wider and shorter than the non-cleft side. There was no significant difference in the chondroblast, chondrocyte and total cellular number in the lower lateral cartilage of the cleft and non cleft sides. There was significantly less glycosaminoglycan content in the ground matrix of the lower lateral cartilage on the cleft side. To conclude: The deficient content of the ground matrix of the lower lateral cartilage of the cleft side allowed the external deformational force to change the dimensions of the lateral crus. This proves that both the intrinsic and extrinsic factors play a role in deformity. Correction will necessitate both sutures techniques for repositioning and cartilage grafts for augmentation