The study will evaluate the efficacy and safety of sunitinib (Arm A), given at 37.5 mg orally once daily, compared to sorafenib (Arm B), given orally at 400 mg twice daily, in patients with inoperable liver cancer. A total number of 1200 patients will be enrolled, 600 on Arm A and 600 on Arm B. Study treatment may be adjusted based on patient tolerance. and will be given until disease progression, occurrence of unacceptable toxicity, or other withdrawal criteria are met. After discontinuation of study treatment, patients will be followed up in order to collect information on further antineoplastic therapy and survival.