We reported the synthesis, characterization, and field-effect transistor properties of two diketopyrrolopyrrole (DPP)-based pi-conjugated copolymers PNDF3-T-DPP and PNDF3-BT-DPP by introducing naphtho[1,2-b;5,6-b']difuran (NDF3) or NDF3 bridged with alkylthienyl as the donor unit. Compared with PNDF3-T-DPP, the incorporation of a short pi-conjugated thiophene spacer into PNDF3-BT-DPP resulted in a "wave" shape molecular backbone, leading to a poorer ordered structure and lower charge carrier transport of the polymer in the thin film, though improved the solubility and processability. On the other hand, by replacing NDF3 with its sulfur analogues, naphtho[1,2-b;5,6-b']dithiophene (NDT3), the resulting NDT3-based polymers possessed poor solubility and twisty spatial structure, which lead to lower hole mobilities. In contrast, PNDF3-T-DPP and PNDF3-BT-DPP exhibited excellent hole mobility when used as the active layer in organic field-effect transistors (OFETs) devices. The highest hole mobilities reached to 0.24 and 0.11 cm(2) V-4 s(-1) for PNDF3-T-DPP and PNDF3-BT-DPP respectively, even without thermal annealing. Higher hole mobilities of up to 0.56 and 0.35 cm(2) V-1 s(-1) were obtained when annealed at 160 degrees C. These features in the present polymers offer great interest of using NDF3 moiety as the building block for semiconducting polymers and give new insight into the design of a new class of semiconducting polymers.