The aim was to assess coronary atherosclerosis, plaque morphology and associations to cardiovascular risk factors and epicardial adipose tissue (EAT) in patients with long duration of type 1 diabetes mellitus (T1DM). Eighty-eight patients with ≥ 45 year T1DM duration and 60 controls underwent coronary CT angiography (CCTA) for evaluation of coronary artery plaque volume (total, calcified or mixed/soft), coronary artery calcification score (CAC) and EAT. Plaques were detected in 75 (85%) T1DM patients and 28 (47%) controls, p < 0.01. Median (interquartile range) plaque volume (mm ) in T1DM vs. controls was: 21.0 (1.0-66.0) vs. 0.2 (0.0-7.1), p < 0.01 for calcified, 0.0 (0.0-8.7) vs. 0.0 (0.0-0.0), p < 0.01 for soft/mixed and 29.5 (3.9-95.8) vs. 0.4 (0.0-7.4), p < 0.01 for total plaque volume. Median CAC was 128 (13-671) vs. 1 (0.0-39.0), p < 0.01 in T1DM vs. controls. Median EAT volume did not differ between the groups; 52.3 (36.1-65.5) cm vs. 55 (38.3-79.6), p = 0.20. No association between CAC or plaque volumes and EAT were observed. Low time-weighted LDL-cholesterol and HbA1c for 30 years were associated with having plaque volume < 25th percentile, OR (95% CI) 0.18 (0.05-0.70), p = 0.01 and 0.45 (0.20-1.00), p < 0.05, respectively. Time-weighted LDL-c was linearly associated with CAC (beta 0.82 (95% CI 0.03-1.62), p = 0.04) and total plaque volume (beta 0.77 (95% CI 0.19-1.36), p = 0.01). Long-term survivors of T1DM have a higher prevalence of coronary atherosclerosis compared to controls. Low LDL-cholesterol and HbA1c over time have a protective effect on coronary atherosclerosis. EAT volume was not associated with coronary atherosclerosis in T1DM patients.