The microwave spectrum of F 2CCCHF has been studied from the 8- to 26-GHz region, with c-type, Q- and R-branch transitions being assigned for the ground vibrational state. The rotational constants obtained are: A = 9360.050(5) MHz, B = 1739.1516(6) MHz, and C = 1554.2665(5) MHz. The dipole moments determined from the Stark effect are: μa = 0.510(6) D, μc = 1.40(3) D, and μtotal = 1.49(3) D. The molecular structure which reproduces the observed moments of inertia has been determined. The structural parameters of allene and fluorine-substituted allenes are compared. The systematic changes that occur in the structural parameters are found as the number of substituted fluorine atoms increases.