Agenesis and hypoplasia of left-sided pulmonary artery anomalies have been infrequently reported. The majority of cases are diagnosed in childhood, but occasionally some asymptomatic cases are first recognised in adulthood when detected by an abnormal chest radiograph. We report a twenty-one year old female patient with left pulmonary artery agenesis who was asymptomatic till adulthood, but presented with mild respiratory symptoms and an abnormal chest X-ray. A contrast enhanced computerised tomography (CECT) scan helped to establish the diagnosis. Early diagnosis of this condition is essential to avert potentially lethal complications.