Objective . Symptoms of pertussis-associated pneumonia and pneumonia due to other organisms often overlap. Recognizing pertussis-associated pneumonia during the paroxysmal stage in hospitalized patients may be challenging.  Therefore, delayed diagnosis often occurs. Reports on pertussis-associated pneumonia among infants and children are still limited.  We investigated clinical, laboratory, and chest X-ray features of pertussis-associated pneumonia, and compared them with pneumonia due to other organisms among infants and children.  
Method. This cross-sectional study was conducted by reviewing medical records of patients aged less than five years old who were diagnosed with pertussis-associated pneumonia and pneumonia at dr. Mohammad Hoesin Hospital's pediatric ward Palembang from April 2018 – March 2019. Statistical analysis for significance of difference between age, sex, clinical features, laboratory and chest X-ray result was done using chi square analysis.
Results. Overall, we found 74 cases of pneumonia and pertussis-associated pneumonia during the study period.  Twenty four cases of pertussis-associated pneumonia and fifty cases pneumonia. The median ages were two months old in pertussis-associated pneumonia and 4.5 months old in control group; males were predominant compared to females.  Significant clinical features in pertussis-associated pneumonia were paroxysmal cough (p=0.00), whoop inspiration (p=0.00), post-cough vomiting (p=0.00) and absence of fever (p=0.00). Tachypnea (p=0.053) were more frequently found in pneumonia patient. Significant laboratory findings in pertussis-associated pneumonia were elevated of lymphocytes (median 50%, p=0.003). There was no difference in hemoglobin (mean 11.1 g/L), WBC (median 12.880 cells/mm3), platelet (median 186.385/µL) and C-reactive protein (median 4 mg/L) on both groups. There was no difference in chest X-ray finding on both groups, mostly chest X-ray results were lung infiltrate.  
Conclusion. Pertussis-associated pneumonia should be considered in afebrile patients who come with paroxysmal cough, whoop inspiration, post-cough vomiting, and lymphocytosis. Tachypnea does not always occur in patient with pertussis-associated pneumonia.