The aim of this study was to investigate the severity of infraorbital nerve injury following zygomaticomaxillary complex fractures and to estimate the treatment methods facilitating its functional recovery. A total of 478 patients with unilateral zygomaticomaxillary complex fractures were treated. Infraorbital nerve sensory disturbances were diagnosed in 64·4% of the patients. Injury of the infraorbital nerve was expressed as asymmetry index, which was calculated as a ratio between the affected side and the intact side electric pain detection thresholds at the innervation zone skin before treatment and 14 days, 1, 3, 6 and 12 months postoperatively. A mean asymmetry index of 0·6 ± 0·03 and 1·9 ± 0·5 was registered for 57 (11·9%) patients with hyperalgesia and for 251 (52·5%) patients with hypoalgesia, respectively. As a result of retrospective analysis of infraorbital nerve sensory disturbances and its functional recovery, infraorbital nerve injury severity was classified as mild, moderate and severe. It was found that the dynamics and outcome of the functional infraorbital nerve recovery depend on the severity of the injury and the presence of infraorbital canal damage. Function was completely recovered within 3 months after treatment in cases with mild nerve injury. In moderate cases, complete recovery was seen within 6 months and in 34·6% of the severe cases, within a 12-month period after treatment when infraorbital nerve decompression was performed according to the stated indication. Treatment based on infraorbital nerve injury classification offers a better prognosis for complete recovery of the infraorbital nerve function.