The paper reports on a comparative study of poly(3-hexylthiophene) (P3HT) films as well as P3HT organic field effect transistors (OFETs) fabricated by the spin coating and spray coating techniques, using fresh and aged (for 2 months) chloroform solutions. The films obtained from aged solutions contain nanostructured fibers of the polymer. The presence of nanofibers in P3HT thin films affects the performance of the OFETs: charge carrier mobilities in the samples deposited from the aged solutions appeared over one order of magnitude higher than those fabricated using fresh solutions. Particularly high mobilities, exceeding 10−2 cm2 V−1 s−1, were found in spin coated samples deposited from aged solutions. Additionally, the latter samples exhibit a certain degree of anisotropy, associated with the action of centrifugal force during the deposition.