Background— We aimed to quantify the contribution of treatments and risk factors to the decline in coronary heart disease (CHD) mortality in Portugal, 1995 to 2008. Methods and Results— The IMPACT mortality model was used to integrate data on trends in uptake of treatments and exposure to risk factors to explain the CHD mortality variation. Between 1995 and 2008, CHD mortality rates in Portugal decreased by 29% in men and 21% in women aged 25 to 84 years, corresponding to 3760 fewer deaths in 2008 than expected if 1995 mortality rates had persisted. Approximately 92% of the estimated decrease in number of deaths could be explained by the model; the remaining 8% were attributed to changes in unmeasured factors. Approximately 50% of the decrease explained by the model was attributable to an increased uptake of treatments, mainly antihypertensive medication (12%) and initial treatments after an acute myocardial infarction (10%), and 42% to population risk factor reductions, mainly blood pressure (27% in men and 60% in women), total cholesterol (14% in men and 5% in women), and smoking (11% in men). However, these reductions were partially offset by adverse trends in diabetes mellitus (18% in men and 2% in women) and obesity (6% in men and 5% in women) and smoking (2% in women). Conclusions— In this low CHD risk population, modern treatments explained approximately half of the overall decline in CHD deaths. The biggest contributions to the CHD mortality decline came from secular decreases in blood pressure and increases in hypertension treatment.