Breast cancer is a complicated disease that it is accompanied by different symptoms. Diagnosis of this disease is performed by various techniques. Using Radiopharmaceuticals is a new method to diagnose the said tumors. [18F]-FPTT is one of these nuclear medicines for detection of breast cancer. It seems that the binding of the title radiopharmaceutical to the progesterone receptor is the main cause of the breast cancer diagnosis. Studying the electronic properties, stability, reactivity and binding of the title compound to the progesterone receptor are the main purposes of the present research work. In first step, [18F]-FPTT molecular structure is optimized at B3LYP/6-311++G(d,p) level of theory at room temperature. Then, its stability and reactivity properties are calculated by frontier molecular orbitals (FMOs) energies. The global reactivity indices show this medicinal molecule may be interacted with active reagents into the cell such as free radicals. Also, this radiopharmaceutical has a molecular structure with high reactivity and it prefers to interact with nucleophile agents or residues. Analyzing the molecular electrostatic potential (MEP) graph of the compound indicates it prefers to interact with the residues of a receptor by its oxygen atoms. On the other hand, the docking analysis of the ligand-receptor complex shows the steric interactions play the main role in this complex formation. The docking analysis data shows the progesterone receptor (PR) residues containing Arg 899 [B], Phe 895 [A], Phe 895 [B], Ser 898 [B], Ser 910 [A], Ile 896 [A], Ser 898 [A], Ile 896 [B], Val 903 [B], Glu 911 [A], Ser 902 [B], Arg 899 [A] and Glu 904 [B] are the major amino acids participating in the ligand-receptor complex formation. Manuscript profile