Lung cancer is the cause of more than 150,000 deaths annually in the United States. Early and accurate detection of lung tumors with Positron Emission Tomography has enhanced lung tumor diagnosis. However, respiratory motion during the imaging period of PET results in the reduction of accuracy of detection due to blurring of the images. Chest motion can serve as a surrogate for tracking the motion of the tumor. For tracking chest motion, an optical laser system was designed which tracks the motion of a patterned card placed on the chest by illuminating the pattern with two structured light sources, generating 8 positional markers. The position of markers is used to determine the vertical, translational, and rotational motion of the card. Information from the markers is used to decide whether the patient's breath is abnormal compared to their normal breathing pattern. The system is developed with an inexpensive web-camera and two low-cost laser pointers. The experiments were carried out using a dynamic phantom developed in-house, to simulate chest movement with different amplitudes and breathing periods. Motion of the phantom was tracked by the system developed and also by a pressure transducer for comparison. The studies showed a correlation of 96.6% between the respiratory tracking waveforms by the two systems, demonstrating the capability of the system. Unlike the pressure transducer method, the new system tracks motion in 3 dimensions. The developed system also demonstrates the ability to track a sliding motion of the patient in the direction parallel to the bed and provides the potential to stop the PET scan in case of such motion.