It is often difficult to determine the actual site of origin of tumours originating in the sino-nasal region, and a uniform classification system that covers all tumours in this area is warranted. A retrospective series of 165 consecutive patients with sino-nasal carcinoma, treated and followed at the Aarhus University Hospital between 1963 and 1991, was evaluated and T-staged according to the Lederman classification. The 80 maxillary antrum carcinomas were also staged according to the UICC 1997 system. In univariate analysis, the UICC T-classification was prognostic for locoregional tumour control and disease-specific survival. However, when adjusted for covariates (gender and nodal involvement) in a multivariate analysis, the UICC classification was not a significant independent prognostic parameter. In contrast, the Lederman T-classification was prognostic both in univariate and multivariate analysis. The Lederman T-classification was more prognostic for locoregional control and disease-specific survival than the UICC TNM classification. In addition, the Lederman classification is easy to use and has a broader applicability as it covers all sites in the sino-nasal area.