Since primary photons can provide information concerning the position of radioisotope (RI) accumulation and the energy of the photons, it would seem reasonable to vary the position and width of the energy window depending on the type of RI and the energy resolution of the detector to collect as many of the primary photons as possible. We propose a method for determining energy window width and position for scintigraphic imaging to collect as many of the primary photons as possible, and studied the influence on the Triple Energy Window (TEW) scatter compensation method of setting such energy window levels for 99mTc (single photopeak) and 201Tl (multiple photopeaks) using detector with different energy resolution through simulation. The Monte Carlo simulations were verified by comparing the regional energy spectrum at the phantom obtained from the simulation against experimental measurements. The energy window with our proposed method for 99mTc is 20% and 47.3% for 201Tl using gamma camera, and 9.8% for 99mTc using a semiconductor detector with a theorized energy resolution of 7.0 keV.