Opioid analgesics are fundamental to pharmacotherapy of cancer pain. Significant and the most freguent constriction for their use may be adverse effects from gastro-intestinal system. Unlike other side effects, constipation does not cease but augments along with the time of opioid therapy. In diagnostics of bowel disorders in cancer patients it should be always considered all the coexisting causes, as opioids usually are only one of several of them. To quantify patient’s subjective assessment of the intensity of constipation, the scales like BFI (Bowel Function Index) or PAC-SYM (The Patient Assessment of Constipation Symptoms) are used. Opioid- induced bowel dysfunction entails decrease in quality of life, increase of healthcare expenses and may pose a barrier for successful opioid treatment. All opioid analgesics bring about constipation. There have been used formulations consisting opioid antagonist (methylnaltrexone) and oral composite preparations (e.g. methylnaltrexone, naloxone) for treatment and preventing of opioid-induced constipation in the last years.