BACKGROUND Although we have epidemiological information on primary immunodeficiencies (PID), the available information is meager in Mexico. OBJECTIVE To provide epidemiological information on the delay in the diagnosis of PID and its correlation to chronic lung damage. METHODS A retrospective, analytical study was done in patients 0-18 year old age diagnosed with PID for 11 years at the HIMFG (Hospital Infantil de Mexico Federico Gomez). The variables studied were: age at symptom onset, age at diagnosis, time from onset of symptoms to diagnosis, number of previous pneumonias and studies with radiographic chronic lung damage data. RESULTS 48 patients were obtained after meeting inclusion criteria; 33 showed lung damage at diagnosis, antibody deficiency being the most affected group. Relating age of onset of symptoms and the time difference of the onset of symptoms to diagnosis showed a strong correlation (p < 0.001, Rho > 0.80). A moderate correlation between the observed time difference vs number of pneumonias (p=0.005, Rho=0.495) and correlation between number of pneumonia and lung damage was highly significant (p <0.001, Rho=0.704). CONCLUSIONS A strong relationship between the elapsed time from onset of symptoms and the number of pneumonia with lung injury time was found. So, the recurrent pneumonia (> 2) must make suspect the diagnosis of PID, as recommended in the literature.