We present the PET/CT findings of extensive disseminated genital herpes simplex virus infection in a 29-year-old woman known with disseminated anaplastic lymphoma kinase-mutated nonsmall lung cancer. PET/CT revealed extensive involvement of the outer and inner genitalia, multiple lymph nodes extending from the porta hepatis to the groins, and involvement of the liver. Disseminated herpes simplex virus infection is well described in neonates and immunocompromised individuals but very rare in immunocompetent adults as was the case with this patient.