This case report describes a 13-year-old boy with diffuse microvascular pulmonary arteriovenous malformations, in whom total anomalous pulmonary venous drainage had been corrected surgically in the newborn period. Contrast transesophageal echocardiography, cardiac catheterization and a lung perfusion scan suggested, and lung biopsy confirmed the diagnosis in our patient. Treatment with nifedipin was commenced. Conclusion: This case illustrates the diagnostic difficulties with this rare malformation.