BACKGROUND AND AIMS: Patients with head and neck cancer (HNC) are often malnourished with a low muscular mass at the outset of management. This is thought to be mainly due to poor nutritional intake. The aim of this study was to assess the correlation between tumor metabolic activity, inflammatory status and body composition in HNC patients. MATERIALS AND METHODS: This retrospective study included 112 patients with HNC. Tumor metabolic activity was assessed using the total lesion glycolysis (TLG) and maximum standardized uptake value (SUVmax). Body composition was measured by the third cervical vertebra skeletal muscle index (C3 SMI). Systemic inflammation was measured by the modified Glasgow Prognostic Score (mGPS) and the neutrophil-to-lymphocyte ratio (NLR). Nutritional status was assessed by the Nutritional Risk Index (NRI). RESULTS: The majority of patients had advanced tumor stage (75 %). Malnutrition was found in 39.3 % (NRI), and systemic inflammation in 44.7 % (mGPS) and 41.1 % (NLR) of patients. High TLG was associated. with low C3 SMI (p = 0.021), low NRI (p = 0.01), high mGPS (p = 0.001), and high NLR (p = 0.003). A high NLR was associated with a low C3 SMI (p = 0.046) and low body mass index (BMI) (p = 0.01). CONCLUSION: Our study establishes a relationship between the high metabolic activity of tumor, the loss of muscle mass, and increased systemic inflammation.