This study aimed to evaluate the feasibility of using 99mTc-HYNIC-Glu(PEG4-oncoFAPi)2 (denoted as 99mTc-H-PoFP2), a novel 99mTc-labeled radiopharmaceutical that targets fibroblast activation protein (FAP), for single-photon emission computed tomography (SPECT) imaging of pulmonary fibrosis in a mouse model and preliminary clinical studies. The gene discussed is FAP; the disease is pulmonary fibrosis.