Background: The most common site of sinonasal and paranasal carcinoma is the maxillary sinus, which accounts for 60-70 percent of all cases. Squamous cell carcinoma (SCC) is the most common histopathological type, accounting for 60–75% . Infiltration of the skull base and/or orbit is one of the complications of such tumours which can have a negative impact on one's quality of life.Objective: The study looked at the epidemiological characteristics and treatment outcomes of patients with maxillary sinus squamous cell carcinoma (MxSSCC) with skull base and/or orbital invasion who were admitted to Mansoura Clinical Oncology and Nuclear Medicine Department and Tanta Clinical Oncology and Nuclear Medicine Department for treatment between January 2000 and December 2018. Patients and methods: This is a retrospective study. Thirteen patient records fulfilled the eligibility criteria of our study. Females were slightly more in number (7 patients (53.8%). The majority of the cases were of age between 40-69 years (N= 11 patients representing 84.6%). Radiotherapy (RT) was the main line of treatment. It was used as the definitive line in ten patients (76.9%) and surgery with postoperative radiotherapy (PORT) was used in (N=3, 23.1%) patients. Results: 5-years overall survival (OAS) of patients with skull base and/or orbital invasion was 15.4% while 2-years progression-free survival (PFS) was 30.8%.Conclusion: This study highlights the effect of the skull base and/or orbital invasion on OAS and PFS of patients with MxSSCC.