A 68-year-old male presented with right shoulder pain for the last 4 weeks. Thorax CT revealed a mass at the level of right upper lobar bronchus in the lung. Bronchoscopic biopsy showed small cell lung cancer. FDG-PET/CT was ordered in order to stage the tumor. PET/CT images demonstrated increased FDG metabolism at the primary tumor with multiple metastatic lymphadenopathies and liver metastases. Additionally, there was widespread heterogenous FDG uptake in the axial skeleton reminiscent of bone marrow metastases. Complete blood count was consistent with mild thrombocytopenia (101,000 per microliter). A trephine biopsy from the posterior iliac crest done when the thrombocyte count dropped to 49,000 after one week proved that there was bone marrow involvement with small cell lung cancer. This case beautifully illustrates that PET/CT heralded bone marrow involvement before we suspected from complete blood count.