Cancer, being in fact a generalized disease involving the whole organism, is most frequently associated with metabolic deregulation, a latent inflammatory state and anorexia of various degrees. The pathogenesis of this disorder is complex, with multiple dilemmas remaining unsolved. The clinical consequences of the above-mentioned disturbances include cancer-related cachexia and anorexia-cachexia syndrome. These complex clinical entities worsen the prognosis, and lead to deterioration of the quality of life and performance status, and thus require multimodal treatment. Optimal therapy should include nutritional support coupled with pharmacotherapy targeted at underlying pathomechanisms of cachexia. Nevertheless, many issues still need explanation, and efficacious and comprehensive therapy of cancer-related cachexia remains a future objective.