Background: This study was designed to assess right ventricular (RV) systolic function in cancer patients. Methods and Results: Left ventricle (LV) and free-wall RV longitudinal strain were analysed prior and after 6 months of treatment (at 68 patients), using a vendor-independent software, together with left ventricular ejection fraction (LVEF), tricuspid annulus plane systolic excursion and RV fractional area change. Cancer therapy-related cardiac dysfunction was defined as a LVEF drop of >10% to <53%. Both LVEF fraction (59±7% vs. 55±8%, p<0.0001) and LV longitudinal strain (-19.7±2.5% vs. -17.1±2.6%, p<0.0001) were reduced.Cancer therapy-related cardiac dysfunction was detected in 20 patients (29%). In 15 out of these 20 patients (75%), a concomitant relative reduction in free-wall RV longitudinal strain magnitude by 17±7% was detected. A relative drop of RV longitudinal strain >17% had a sensitivity of 55% and a specificity of 70% to identify patients with cancer treatment. Conclusions: GLS analysis allows the identification of subclinical RV dysfunction appearing in the course of cancer treatment when conventional indices of RV dysfunction function are unaffected.