Electrical properties of single-gated (bottom-gated or top-gated) and double-gated (DG) organic thin-film transistors (OTFTs) are systematically investigated in terms of threshold voltage (V th), subthreshold slope, and I ON/OFF. We found that the device structure has significant impacts on the aforementioned electrical properties and the operation modes in a poly-3-hexyl thiophene DG OTFT. An empirical electrostatic potential model is employed to describe well V th behaviors of DG OTFTs in different modulation schemes. In addition, selective active-area coating in OTFTs is realized using an inkjet printing process, and consequently, parasitic leakage is much suppressed.