OBJECTIVE: The present study compared heart rate variability (HRV) parameters in patients with coronary artery ectasia (CAE) and coronary artery disease (CAD). METHODS: The study population consisted of 60 consecutive patients with CAE (14 women; mean age 51.63+/-7.44 years), 60 consecutive patients with CA (15 women; mean age 53.67+/-9.31 years), and 59 healthy individuals (13 women; mean age 52.85+/-8.19 years). Electrocardiograms, 24-hour Holter analyses, and routine biochemical tests were performed, and clinical characteristics were evaluated. Coronary angiography images were analyzed. Time-domain HRV parameters, including the standard deviation (SD) of normal-to-normal intervals (SDNN) and the root mean square of difference in successive normal-to-normal intervals (RMSSD) were evaluated, as were frequency-domain HRV parameters including low-frequency (LF), very low-frequency (VLF), high-frequency (HF), the proportion derived by dividing low- and high-frequency (LF/HF), and total power (TP). RESULTS: SDNN was lower in both the CAE and CAD groups, compared to the healthy group (140.85+/-44.21, 96.51+/-31.28, and 181.05+/-48.67, respectively). A significant difference in RMSSD values among the groups was determined (p=0.004). Significantly decreased VLF and HF values were found in the CAE group, compared with the healthy group (VLF p<0.001; HF, p=0.007). TP, VLF, and HF values were significantly lower (p<0.001, p<0.001, and p<0.001, respectively), but LF and LF/HF values were significantly higher (p<0.001 for both) in the CAD group than in the healthy group. TP values were significantly higher (p<0.001), and LF and LF/HF values were lower in the CAE group, compared with the CAD group (p<0.001 for both). CONCLUSION: A decrease in vagal modulation or an increase in sympathetic activity of cardiac function, assessed by HRV analysis, is worse in patients with CAD than in patients with CAE.