BACKGROUND The fat attenuation index (FAI) of pericoronary adipose tissue is associated with coronary inflammatory reactions. OBJECTIVE This study aimed to analyze the difference in the FAI ratio between pericoronary adipose tissue volume and aortic root epicardial adipose tissue volume (AO-EATV) using computed tomography (CT) in various plaques. METHODS In total, 645 coronary artery CT angiogram images from 215 patients were collected. The types and number of coronary plaques were recorded, and the plaque volume and pericoronary FAI of each branch were compared between the groups. The ratio of the FAI in branches with or without plaques to the AO-EATV was determined and statistically analyzed between the groups. RESULTS No significant difference in the plaque volume among the left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA) (P > 0.05) as well as in the FAI was observed among various plaque groups (P > 0.05). FAI[LAD]/AO-EATV was in the following order: noncalcified plaques (0.70 ± 0.06) < mixed plaques (0.72 ± 0.06) < calcified plaques (0.73 ± 0.08) < no plaques (0.74 ± 0.07); FAI[LCX]/AOEATV was in the following order: noncalcified plaques (0.71 ± 0.06) < mixed plaques (0.72 ± 0.08) < calcified plaques (0.73 ± 0.09) < no plaques (0.74 ± 0.06); and FAI[RCA]/AO-EATV was in the following order: noncalcified plaques (0.71 ± 0.06) < mixed plaques (0.73 ± 0.07) < calcified plaques (0.74 ± 0.07) < no plaques (0.75 ± 0.09); the differences were statistically significant in each group (P = 0.041, 0.043, and 0.028, respectively). CONCLUSIONS Compared to simply comparing FAI, FAI/AO-EATV varied in the coronary arteries in various plaque groups. FAI/AO-EATV was lower in noncalcified or mixed plaques and was associated with coronary inflammatory reactions.