Intra-arterial treatment has been identified as one of the mainstays in the management of unresectable hepatocellular carcinoma. A thorough knowledge of tumor arterial supply enables selective therapy, which improves both safety and efficacy. The inferior phrenic artery (IPA) is the most common extrahepatic collateral artery that feeds hepatocellular carcinoma. The bilateral IPAs are known to have a specific vascular anatomy. A systemic-to-pulmonary shunt and a gastric branch from the IPAs may be present and should not be confused with tumor blush. The supraceliac aorta and celiac trunk are the common origin sites of the IPAs, and their orifice may be compressed by the diaphragm. Various techniques and catheters are used for catheterization of the IPAs, depending on their origin sites. Because the IPA is normally connected with the intercostal, internal mammary, retroperitoneal, and hepatic arteries, its hemodynamics may be altered when its orifice is occluded. In general, superselective chemoembolization via the target branch of the IPA is safe and effective. When a systemic-to-pulmonary shunt from the IPA is adequately embolized with coils or particles, radioembolization through the IPA can be performed safely in most cases. The cystic artery branches into deep and superficial cystic arteries; deep cystic arteries often supply tumors near the gallbladder. Chemoembolization through the cystic artery is relatively safe, with transient embolic materials. Radioembolization through the cystic artery has been recently tried, with acceptable efficacy and toxicity results, but it requires further investigation. ©RSNA, 2022.