Aim: Right ventricle is a complex part of the heart of which importance hes been neglected so far. Because of the complex geometric structure of right ventricle all non invazive imaging methods evaluating its structure and functions have important restrictions. In this study we investigated the importance of fractional shortening (FS) measured by anatomic M mode in showing right ventricular (RV) functions. Material and Method: 22 patients with atrial septal defect (ASD) (12 female. 10 male; mean age: 47.1 +/- 19.5) were enrolled to study as right ventricle volume overload group (group 1), besides 21 patients with chronic obstructive lung disease (8 female, 13 male; mean age: 50,6 +/- 20,4) were included as rigth ventricular pressure overload group (group 2) and 20 subjects (8 female and 12 male; mean age: 28,4 +/- 7,2) were included as control group. Fractional shortening was estimated using formula: diastolic diameter - systolic diameter /diastolic diameter x 100. The measurements were made from right ventricular annular level, mid ventricular level and RVOT level. Right ventricular ejection fraction was estimated by ellipsoidal method using right ventricle volumes. Results: When groups 1 and 2 were compared to group 3 apart from each other RV EF (%)(34 +/- 9,5 - 64 +/- 5; p<0.016 ve 37 +/- 8,5 - 64 +/- 5; p<0.016), Tricuspit annular FS(%) (32 +/- 5,8 - 48 +/- 5,6: p<0.016 ve 35 +/- 0,1 - 64 +/- 5; p<0.016), RV mid region FS(%)(34 +/- 8,2 - 52 +/- 6,7; p<0.016 ve 34 +/- 8,8 - 52 +/- 6,7; p<0.016) and RVOT FS(%) (37 +/- 9,5 - 58 +/- 3,9; p<0.016 ve 37 +/- 0,2 - 58 +/- 3,9; p<0.01 6) were found different, this difference was statistically significant. Discussion: FS measured by anatomic M mode can be used as an easy applicable and quick method for investigating right ventricular functions.