Two women with insulin-treated diabetes who presented with hyperventilation in the setting of generalized anxiety disorder and panic disorder, respectively, are reported. The symptoms of hyperventilation and hypoglycaemia proved indistinguishable even after successful treatment with a behavioural approach including explanation, breathing retraining, and relaxation. With diabetic patients a cognitive strategy is complicated by conditioning to think in terms of diabetic control and an inability to safely reattribute symptoms to faulty breathing habit because of the risk of ignoring hypoglycaemia.