Pneumothorax: This condition, where air leaks into the space between the lung and chest wall, is the most likely cause of resonance over the lungs upon percussion. The air accumulation leads to hyperresonance due to the increased air density in the thoracic cavity.

Chronic Obstructive Pulmonary Disease (COPD): Conditions like emphysema, which fall under COPD, can lead to hyperinflation of the lungs, resulting in increased resonance upon percussion due to the trapping of air.
Pulmonary Embolism: While not always directly causing resonance, a large pulmonary embolism can lead to areas of lung infarction or atelectasis, potentially altering percussion sounds, though this is less direct than other causes.
Asthma: Similar to COPD, severe asthma attacks can cause hyperinflation of the lungs, leading to increased resonance.

Tension Pneumothorax: A life-threatening condition where the pressure in the thoracic cavity increases due to air accumulation, which can lead to a mediastinal shift and compromise respiratory and cardiac function. It is crucial to identify this condition quickly due to its high mortality rate if not promptly treated.
Lung Cancer with Pneumothorax: Though less common, lung cancer can cause pneumothorax either by directly invading the pleura or by causing a check-valve mechanism leading to air leakage into the pleural space.

Cystic Lung Diseases (e.g., Lymphangioleiomyomatosis, Cystic Fibrosis): These conditions can lead to the formation of cysts or bullae in the lungs, which may cause hyperresonance upon percussion due to the trapped air within these structures.
Pneumatoceles: Air-filled cysts or cavities within the lung, often associated with infections like pneumonia or Staphylococcus aureus, can also lead to increased resonance.