This is a retrospective study of 45 paediatric patients, aged between eight and 18 years, who underwent Type 1 cartilage graft tympanoplasty using conchal cartilage. Middle ear and mastoid volumes of these children were correlated with anatomical and functional outcomes of surgery. Case selection excluded factors such as inflammation, ossicular chain disruption, previous surgery or craniofacial abnormality. Middle ear and mastoid volumes were determined from high-resolution CT scans of petrous temporal bones, using segmentation tool in the Horos picture archiving and communication system viewer software. Assessment of surgical results were made in the sixth postoperative month. Anatomical success, that is closure of the perforation, was adjudged as evident and functional success was determined by closure of air-bone gap to less than 20 dB. It was noted that there was a statistically significant difference between the preoperative mastoid volume of the successful group and the unsuccessful group in terms of closure of the perforation; that is those with larger mastoid volumes had better surgical outcomes. The same was not the case for functional success. Similar results from literature have been quoted, one of them stating that good mastoid volume even compensates for poor Eustachean tube function. Although successful closure of perforation ranges from 70-80%, this may add to the predictability of results.