In most cancer patients, pain is successfully treated with pharmacological measures such as opioid analgesics alone or opioid analgesics combined with adjuvant analgesics (co-analgesics). Opioids for mild-to-moderate pain (formerly called weak opioids) are usually recommended in the treatment of cancer pain of moderate intensity. There is a debate whether the second step of the WHO analgesic ladder, which, in Poland, is composed of opioids such as tramadol, codeine, dihydrocodeine (DHC), is still needed for cancer pain treatment. One of the most interesting and useful drugs in this group is tramadol. Its unique mechanism of action, analgesic efficacy and profile of adverse effects are responsible for its successful use in patients with different types of acute and chronic pain, including neuropathic pain. The aim of this article is to summarize the data regarding pharmacodynamics, pharmacokinetics, possible drug interactions, adverse effects, dosing guidelines, equipotency with other opioid analgesics and clinical studies comparing efficacy, adverse reactions and safety of tramadol to other opioids in cancer pain treatment.