<b><i>Background:</i></b> Correct pre-therapeutic staging of the first primary carcinoma (FPC) and detection of simultaneous second primary carcinomas (SSPCs) decisively influence therapy and prognosis of head and neck squamous cell carcinomas (HNSCC). The aim of this study was to determine the benefit of pre-therapeutic triple endoscopy for detection of SSPC and pre-therapeutic T category. <b><i>Methods:</i></b> A cohort of 234 HNSCC patients with completed triple endoscopy was reviewed, focusing on pre-therapeutic T category and SSPC. Risk stratification for different subsites was evaluated. <b><i>Results:</i></b> The risk for SSPC was 5.56%. FPC of the oral cavity and oropharynx had the highest prevalence of SSPC (46.15%, 38.46%); most SSPCs were found in the hypopharynx. No SSPCs were found in the oral cavity, nasopharynx and oesophagus. Significant results in correct pre-therapeutic T staging have been achieved for the larynx (p = 0.021) and the oropharynx (p = 0.001). <b><i>Conclusions:</i></b> Triple endoscopies seem to be inadequate for SSPC detection in HNSCC patients. Endoscopies of the trachea and oesophagus should be reconsidered. Alternatively, risk-directed endoscopies of the hypopharynx might be performed in patients with oral cancer. For evaluation of resectability, conducting triple endoscopy could be reduced to a single endoscopy because the complication rate is low and pre-therapeutic T staging can be improved.