Background A strategy using coronary artery calcium (CAC) screening to refine coronary heart disease risk assessment in moderately high risk (MHR) subjects (10-year risk 10%-20%) has been suggested. The potential impact of this strategy is unknown. Methods Coronary artery calcium screening strategies focused on MHR subjects were modeled in 2,610 subjects aged 30 to 65 years undergoing Framingham risk scoring and CAC assessment in the Dallas Heart Study. The proportions of subjects eligible for imaging and reclassified from MHR to high risk (HR) (10-year risk >20%) based upon CAC scores were determined. Results Only 1.0% of women and 15.4% of men were at MHR by Framingham risk scoring and thus eligible for imaging, and <0.1% and 1.1% respectively, changed from MHR to HR using a CAC threshold ≥400. Coronary artery calcium imaging targeting MHR subjects was also relatively inefficient (>100 women, 14.3 men scanned per subject reclassified). Restricting to an older age range (45-65 years) or expanding the MHR group to 6% to 20% risk had virtually no impact on risk assessment in women. In a secondary analysis, a proposed imaging strategy targeting promotion of subjects from lower risk to MHR was more efficient and had greater yield than current recommendations targeting promotion from MHR to HR. Conclusions Coronary artery calcium screening strategies focused on MHR subjects will have a negligible impact on risk assessment in women and a modest impact in men. Further studies are needed to optimize the use of CAC screening as an adjunct to coronary heart disease risk assessment, especially for women and those at seemingly lower risk.