Understanding the pathophysiology of diseases is essential for critical thinking and accurate diagnosis. This comprehensive case report collection offers insights into how to arrive at the correct diagnosis by exploring a variety of respiratory-related clinical cases. Covering the full spectrum of pediatric pulmonology--from the upper and lower airways to the pulmonary complications of systemic diseases--this resource provides valuable guidance on topics such as the diverse causes of hypoxemia, differential diagnoses for cough, and strategies for evaluating respiratory distress amidst a range of potential causes, congenital abnormalities, and the lessons learned from the COVID-19 pandemic. Ideal for learners aiming to strengthen their diagnostic reasoning, this compilation connects clinical presentation with underlying mechanisms to improve understanding and patient care.