The 5 cases of salivary duct carcinoma (SDC); very rare, but distinct group of highly malignant salivary gland tumor are presented, and difficulties with pathological and clinical diagnosis is discussed. The SDC developed in single cases in parotid salivary gland, submandibular salivary and in mucosa of maxillary sinus, pyriform fossa and oral cavity (check). In 3 cases the second malignant tumor was present--synchronously (SDC + pleomorphic adenoma in parotid gland; SDC + squamous cell carcinoma in hypopharynx) or metachroneously (squamous cell carcinoma of upper lip followed by SDC). In one case the high levels of PSA suggesting of metastases from unknown primary within the prostate gland, or PSA expression related to SDC was observed. The four patients received radical treatment - surgical resection followed by radiotherapy; in one case only palliative treatment was applied, due to patient's poor general condition and high advancement of the primary disease. The observation ranged from 10 to 77 months (average time--31 months). The one patient died 13 months after diagnosis and palliative treatment. The three patients are alive with distant metastases to the lung and bones (77, 38 and 18 months after primary treatment was completed). Only one patient with 10 months observation after treatment is living without symptoms of recurrence or metastases.