BACKGROUND: It is not known whether there is a sex difference in the association between perivascular inflammation and plaque vulnerability. The aim of this study was to investigate the sex-specific association between perivascular inflammation and plaque vulnerability. METHODS: Patients who underwent coronary computed tomography angiography and optical coherence tomography were enrolled. All images were analyzed at a core laboratory. The level of perivascular inflammation was assessed by pericoronary adipose tissue attenuation on computed tomography angiography and the level of plaque vulnerability by optical coherence tomography. Patients were classified into 3 groups according to tertile levels of culprit vessel pericoronary adipose tissue attenuation (low inflammation, ≤−73.1 Hounsfield units; moderate inflammation, −73.0 to −67.0 Hounsfield units; or high inflammation, ≥−66.9 Hounsfield units). RESULTS: A total of 968 lesions in 409 patients were included: 184 lesions in 82 women (2.2 plaques per patient) and 784 lesions in 327 men (2.4 plaques per patient). Women were older (median age, 71 versus 65 years; P <0.001) and had less severe coronary artery disease with a lower plaque burden than men. In women, it was found that perivascular inflammation was significantly associated with plaque vulnerability, with a higher prevalence of thin-cap fibroatheroma and greater macrophage grades in the high inflammation group compared with the low inflammation group (low versus moderate versus high inflammation in women: 18.5% versus 31.8% versus 46.9%, P =0.002 for low versus high inflammation; 3 versus 4 versus 12, P <0.001 for low versus high inflammation, respectively). However, no significant differences were observed among the 3 groups in men. CONCLUSIONS: Perivascular inflammation was associated with a higher prevalence of thin-cap fibroatheroma and more significant macrophage accumulation in women but not in men. REGISTRATION: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT04523194.