Acute bronchitis - No infiltrates on the CXR.
Sinusitis - Sinus tenderness, post nasl drip.
Asthma- No infiltrates on chest Xray.
COPD - No infiltrates on chest Xray.
Empyema - CXR showing features of pleural effusion, inflammatory markers on thoracocentesis.
Pertussis - productive cough for weeks, nasopharyngeal aspirate aids in diagnosis.
Lung abscess - CXR showing signs of lung abscess.
Pulmonary embolus - A high degree of suspicion should be kept for pulmonary embolus. Chest X ray may be normal.
Malignancy - CT scan and biopsy are helpful in ruling out malignancy.
Vasculitis - Systemic manifestations of collagen vascular disease may be seen.
Bronchiolitis obliterans with organizing pneumonia should be suspected in patients who don't respond to antibiotics treatment.
Congestive heart failure - Bilateral pulmonary edema, involving more the lower lung fields.
Gastroesophageal reflux disease - Normal chest Xray, symptoms worsening during night.
Endocarditis with septic pulmonary emboli
Upper respiratory tract<unk> 
Influenza
Aspiration pneumonia bacterial infection differential diagnosis
Bacterial pneumonia differential diagnosis
Aspiration pneumonia other diagnostic studies
Bacterial pneumonia other diagnostic studies
Air embolism differential diagnosis
Acute bronchitis differential diagnosis
Lung abscess other diagnostic studies
Pleural effusion differential diagnosis