Histopathological data correlated the presence of thin‐cap fibroatheroma (TCFA) with adverse cardiovascular events. Intravascular optical coherence tomography (iOCT) is currently the only imaging modality with sufficiently high axial resolution (∼15 μm) that allows direct fibrous‐cap (FC) assessment in vivo. iOCT quantification of TCFA has been validated, but the assessment of a single cross‐sectional image does not depict the complexity of the atherosclerotic plaque. We present two cases that illustrate the importance of three‐dimensional volumetric quantification of the FC capitalizing on the properties of frequency‐domain iOCT. © 2012 Wiley Periodicals, Inc.