Primary hyperaldosteronism (PHA) represents less than 1 to 2% of all causes of hypertension (HT). We report 2 cases of primary hyperaldosteronism which emphasize the difficulty of distinguishing neoplastic PHA from idiopathic PHA, observed in a 60-year-old woman and a 42-year old woman, respectively. In both cases, the diagnosis of PHA was suggested by marked hypokalaemia with inappropriate potassium excretion and was confirmed by hyperaldosteronaemia and low and poorly stimulated renin activity. In the first case, computed tomography showed nodular hyperplasia of the 2 adrenal glands. The patient was treated with spironolactone and calcium channel blockers which controlled blood pressure and serum potassium. In the second case, computed tomography and magnetic resonance imaging revealed an adrenocortical adenoma confirmed by pathological examination after the operation. The diagnosis of primary hyperaldosteronism is based on three steps: detection, positive diagnosis and aetiological diagnosis. Detection is essentially based on demonstration of hypokalaemia. Positive diagnosis is based on demonstration of elevated aldosterone secretion with inhibited renin secretion. The aetiological diagnosis is dominated by the differentiation between Conn's adenoma and bilateral adrenal hyperplasia, which has therapeutic implications.