The quasars, 0420-014, 0748+126 and 2251+158 (3C 454.3), have been observed at 1.3 cm with a global VLBI network. We have obtained the hybrid maps of the quasars at sub-milliarcsecond resolution. The brightness distribution is revealed in their nuclear regions. The observed data are fitted with a small number of Gaussian components. 2251+158 shows a core-jet structure, and its nuclear region is elongated in the direction PA= -130o. The jet is curved. Its observations at the epoch 1992.9 show it to be in the course of a large burst, accompanied by several smaller ones. The strongest component has a flux of ~ 4.11 Jy (67% of the total detected flux), mostly from an area of 0.16 x 0.01 mas. Doppler boosting is probably responsible for raising the brightness temperature up to 2.6 x 1012 K.