A 55-year-old woman with newly diagnosed hepatocellular carcinoma (HCC) was hospitalized in our department for the evaluation of selective internal radiotherapy (SIRT), which consists of an angiography, an intra-arterial technetium (Tc)-99m-macroaggregated albumin application and Tc-99m sulfur colloid scintigraphy to assess liver function. Besides the modest intratumoral tracer accumulation, F-18-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) imaging showed two intense focal cuneiform splenic FDG accumulations which turned out to be splenic infarctions. Four months later, both hypermetabolic foci were completely regressive in the first follow-up PET/CT after SIRT. This is the first report of a complete metabolic regression of splenic infarctions within just 4 months, whereas regression on CT is commonly seen after more than 2 years.