A patient with diffuse large cell lymphoma involving the interventricular septum and the inferior ventricular wall was imaged with a simultaneous dual-isotope single-photon emission tomography (SPET) acquisition technique, using the radiotracers technetium-99m hexakis 2-methoxyisobutylisonitrile (sestamibi) and gallium-67 citrate, in conjunction with echocardiography, prior to and following the first course of chemotherapy. Simultaneous acquisition--with the advantage of displaying corresponding sets of SPET slices without any need for position correction--, supplemented by echocardiography, increased the accuracy of evaluation of the extent of disease and response to treatment.