Background: Coronary computed tomography angiography (CTA) allows the evaluation of coronary plaque volume and low attenuation (lipid-rich) component, for plaque vulnerability assessment. Purpose: To determine the effect of iterative reconstruction (IR) on coronary plaque volume and composition. Material and Methods: Consecutive patients without coronary artery disease were prospectively enrolled for 256-slice CT. Images were reconstructed with both filtered back projection (FBP) and a hybrid IR algorithm (iDose(4), Philips) levels 1, 3, 5, and 7. Coronary plaques were assessed according to predefined Hounsfield unit (HU) attenuation intervals, for total plaque and HU-interval volumes. Results: Fifty-three patients (mean age, 53.6 years) were included. Noise was significantly decreased and signal-to-noise ratio (SNR) / contrast-to-noise (CNR) were both significantly improved at all IR levels in comparison to FBP. Plaque characterization was performed in 41 patients for a total of 125 plaques. Total plaque volume ranged from 104.4 +/- 120.7 to 107.4 +/- 128.9 mm(3) and low attenuation plaque component from 40.5 +/- 54.7 to 43.5 +/- 58.9 mm(3), with no statistically significant differences between all IR levels and FBP (P = 0.786 and P >= 0.078, respectively). Conclusion: IR improved image quality. Total and low attenuation plaque volumes were similar using either IR or FBP.