The purpose of this study is to examine the effect of posture in the sitting and supine positions on ballistocardiography (BCG) measurements by using EMFi (electromechanical film) sensors. The experiment, measuring the subject's electrocardiography (ECG), BCG and carotid pulse (CP) signal, was repeated in the sitting and different horizontal positions. Additionally, the duration and the amplitudes of the BCG and CP signal components were studied. Certain properties of BCG differed significantly in the sitting and horizontal positions. Amplitudes of measured signals were larger, and time intervals were greater in the sitting position compared to the supine position. Thus, posture significantly influences cardiac performance evaluated by BCG. Sitting and supine positions are clearly distinguishable in the BCG signal. This provides new methods for evaluation of the hemodynamic changes induced by the body position.