In this study, show-jumping horses (n = 80) and Arabian race horses (n = 80) from different work groups were examined, with the guidance of 2-D, by M-Mode echocardiography, to establish the reference values and to determine the differences in the cardiac structural measurements. Measurements were performed in four different planes by obtaining M-Mode cross-sections from M. papillaris, C. tendinei, mitral valves and aorta root levels, with the guidance of 2-D in the 4th intercostal space. Left ventricle, right ventricle, left atrium, aorta root, interventriculer septum, left ventricle posterior wall and heart wall movements were observed and end-systolic and end-diastolic diameters with left ventricle function evaluations were performed. Subsequently, all of these values were compared between the two groups. The results indicated statistical significance of P < 0.001 in end-diastolic volume (EDV) and ejection fraction (EF), and P < 0.005 in diastolic left ventricle internal diameter (LVIDd), diastolic interventricular septum thickness (IVSd), diastolic right ventricle internal diameter (RVd), diastolic aorta internal diameter (Aod), fractional shortening (FS) and cardiac output (CO). It has been concluded that Arabian race horses are more advantageous with their powerful left ventricle functions, while show-jumping horses have the benefit of possessing wider left ventricles, indicating the probability that exercise improves the left ventricle functions in horses.