We carry out spin-polarized positron lifetime calculations for ferromagnetic metals using the electron–positron density functional theory (DFT). We investigate Fe, Co, and Ni and find that the differences between the positron lifetimes for their minority and majority spins (τ↓ − τ↑) are 11.85, 3.75, and −4.37 ps, respectively. The negative lifetime difference of Ni is presumed to originate from an unlocalized distribution of minority electrons.