A 2-year-old girl with cardiorespiratory distress and suspected pulmonary embolism (PE) was referred for urgent lung perfusion scintigraphy, proven negative for perfusion defects but unexpectedly revealing an enlarged orthotopic thyroid. This finding was, under the circumstances, considered as suggestive of thyroid storm (TS), subsequently confirmed by thyroid hormones measurement. A (99m)TcO(4)(-) thyroid scan 1 week later showed a homogenously enlarged thyroid with high tracer uptake. Both PE and TS are rare but serious pediatric conditions with partially overlapping presentations. In the present case, the unbounded (99m)Tc fraction avidly taken by the overfunctioning thyroid suggested the correct, clinically unsuspected, diagnosis.