The first aim of the study was to determine the survival rate of the patients with Carcinoma of the Unknown Primary (CUP) in relation to lymph node status and eventual later identification of the primary tumor. To second one was to investigate the impact of PET-CT on identification of the primary tumor. We studied 97 patients sent to our University Medical Center with diagnosis of metastasis of unknown primary tumor between 1.1.1997 and 1.9.2009. All patients had panendoscopy and some had PET-CT at later period. All susceptible patients had a surgery and postoperative radiation therapy. After the completed their treatment they were followed up at ENT department. With preoperative examinations we discovered 48 primary tumors. Only in one case of 13 the PET-CT detected the primary tumor not confirmed with other examination methods. After the treatment we found primary tumors in 10 patients. In 39 patients we didn't discover any primary tumor. The 2-year overall survival for 10 patients with found tumor was 80.0%, the 2-year overall survival for the 39 patients without discovered tumor was 73.8%. The 2-year disease-specific survival for 10 patients with found tumor was 90.0%, the 2-year disease-specific survival for 39 patients without discovered tumor was 81.6%. The 2-year overall survival for high neck level lymph node metastasis group (N = 36) was 80.1%, the 2-year overall survival for low neck level lymph node group (N = 13) was 61.5%. PET-CT method was not particularly useful in detecting primary tumors in patients with metastasis with unknown primary. Patients with high neck level lymph node metastasis had statistically significant better survival.