A thesis on Head and neck cancer focusing on dose planning, salivary gland carcinoma and Single nucleotide polymorphism. For dose planning PET/CT (Positron emissions tomography/computed tomography) with tracer gave more precise information in comparison dose planning with CT. More primary tumours and metastases were found with the acetate tracer than with glucose tracer. Acetate PET/CT also showed larger volume of tumours attributed to lipid metabolism. In a retrospective study salivary gland cancer 5-year overall survival (OS) was 53 %. Salivary gland carcinoma consists of many histopathological groups, the two largest groups being mucoepidermoid carcinoma (MEC) and adenoid cystic carcinoma (ASCC). For ACC, having the best 5-year OS, it was 70 percent. Facial palsy, advanced stage disease, lymph node metastases worsened prognosis. ACC and polymorphous low grade carcinoma (PLGA) expressed c-myc and cyclin D1 to a larger extent than MEC. In squamous cell carcinoma of the head and neck we examined the occurrence of Single Nucleotide polymorphism, SNP. We found that the SNPs in male and female patients differed from each other. In male patients the SNPs were associated with immune response while in female patients the association was to SNPs concerning inflammation. This means that different pathways were engaged in cancer development for men and women. We also found that the SNPs in patients were different from those expressed in the healthy controls.