The aims of the study: The aims of this study were to examine whether there is a difference in the clinical findings of the lesion obtained by coronary angiography and OCT and to examine the association of OCT findings in the decision-making on additional optimization of PCI. Respondents and methods: The research was conducted as a cross-sectional study using historical data. The study included patients who underwent OCT at the Department of Cardiovascular Diseases of the Osijek Clinical Hospital Center from 2021 to 2023. Results: The research involved 62 patients, with a median age of 67. The most common location of the lesion was the LAD, in 52 (84%) cases. Thirty-nine respondents (63%) required additional optimization. Three (5%) patients were recommended for cardiosurgical consultation based on OCT. There was a significant increase in the length of the LAD (Wilcoxon test, P < 0.001), LCx (Wilcoxon test, P < 0.001), and RCA (Wilcoxon test, P = 0.006) as measured by OCT compared to coronary angiography. Regarding proximal width, the values for the LAD (Wilcoxon test, P < 0.001) and RCA (Wilcoxon test, P = 0.03) were significantly higher. Conclusion: The research demonstrated the important role of OCT in clinical practice, particularly in the detailed assessment of coronary artery lesions, management of PCI, and assessment of additional optimization in patients with coronary disease.