To improve contrast-to-noise ratio in a small volume of interest, a combination of parallel- and cone-beam collimator SPECT acquisition and fully 3D iterative reconstruction with a volumetric system model has been developed. The Monte Carlo package SimSET along with a numerical chest phantom with half-ring defect were used to simulate static cardiac SPECT scans. Parallel-beam only, cone-beam only, Jaszczak approach, and our proposed parallel-cone approach were applied in reconstruction. The visual quality of the Jaszczak method and the proposed parallel-cone reconstruction is much better than cone-only reconstruction, and is free of truncation artifacts. Contrast-to-noise ratio, noise, and bias in a small volume-of-interest encompassing the heart have been improved in the proposed parallel- and cone-beam approach, as compared to the other three methods.