Interstitial lung diseases (ILDs) include over 200 conditions affecting the lung parenchyma. ILDs are classified as non-fibrosing or fibrosing, with many fibrosing forms initially presenting as inflammatory and only progressing to fibrosis over time. Diagnosing ILDs is challenging due to their variety and rarity, with CT scans playing a key role in the process, though final diagnoses are made through multidisciplinary team discussions. Biopsies are generally avoided unless CT results are inconclusive or conflict with clinical findings, emphasizing the importance of a thorough CT protocol and approach. The systematic evaluation of CT scans for suspected ILD involves a three-step approach: first, describing parenchymal abnormalities; second, assessing extraparenchymal findings such as pleural and mediastinal structures; and finally, determining the differential diagnosis based on the distribution of these findings. Parenchymal abnormalities are divided into decreased lung densities (e.g., emphysema, cysts) and increased lung densities (e.g., ground-glass opacities, consolidations). These findings should follow the Fleischner Society’s terminology for consistency. Extraparenchymal features include abnormalities in the airways, pleura, and mediastinum, as well as possible extra-thoracic manifestations in organs such as liver or spleen. The distribution of findings, whether in different lung zones or within the secondary pulmonary lobule, plays a key role in diagnosing specific diseases, such as differentiating Langerhans cell histiocytosis from lymphangioleiomyomatosis based on cyst location.