Respiratory system consists of two major parts. Nasal passage and trachea are part of upper airways and lungs are part of lower airways. Inhaled air passes from upper tract to the lower tract. When the air reaches the lung tissue, inhaled oxygen enters the blood stream and the carbon dioxide leaves the blood to be exhaled out. Carbon dioxide is a metabolic waste of the body. Cats suffering from lung disease cough and have difficulty in breathing. They seem tired even after least exercise. Radiographic techniques such as X-rays are helpful in diagnosis of any problem in the heart. Major problems of respiratory problems include pneumonia, heartworms, lung cancer and asthma.