Squamous cell carcinomas (SCCs) of the upper aerodigestive tract are one of the most common tumors in Poland. They are rarely diagnosed in early stages, hence survival is poor. The author presents histological features of neoplastic transformation within squamous epithelium (dysplasia, in situ carcinoma, intraepithelial neoplasia) and the evolution of grading systems. Then, the risk factors, precancerous lesions, and precancerous conditions of oral, oropharyngeal, laryngeal, laryngopharyngeal, sinonasal, and nasopharyngeal SCCs are discussed. The genetic background of carcinogenesis in head and neck region and perspectives of early diagnosis are outlined.