The possibility of non-inductive build-up of a hot plasma by X-wave ECH/ECCD to remove initial high loop-voltage stage from start-up of fusion tokamaks is theoretically investigated, using ITER parameters. There are two injection methods for X-wave ECH/ECCD in ITER start-up plasmas. The first is oblique X-wave injection from the low-field side, referred to as the DX method. For the low density start-up plasma at n(e) approximate to 1.0 x 10(19) m(-3), the wave with omega/2 pi = 200 GHz and N-vertical bar vertical bar similar to 0.6 is damped away via cyclotron resonance absorption before encountering the cyclotron cutoff layer when the electron temperature is as high as T-e > 170 eV. The wave power is deposited into the resonance electrons of which parallel velocity is as fast as nu(vertical bar vertical bar) > 2 root 2T(e)/m, which enables an efficient ECCD. The second method is oblique O-wave injection from the low-field side, referred to as the OX method. The waves pass through the ECR layer with negligible power deposition when T-e < 400 eV and are mode-converted into oblique X-waves upon reflection on the inboard wall. The X-waves propagate toward the ECR layer without cutoff, and are cyclotron-damped away even when the temperature is as low as T-e similar to 7 eV. The OX method is appropriate for the initial open field stage and transition stage of the discharge, while the DX method is appropriate for the final tokamak stage, where T-e is high. Discussions are given on the choice of appropriate B-V and location of ECR layer for initiation of closed flux surfaces. Nine model plasmas from an initial open field plasma to a final hot tokamak plasma, consisting of a series of snapshots of a build-up discharge, are generated using an equilibrium theory, enabling estimation of required RF power to drive the current. These investigations suggest that an injection power P-rf similar to 4 MW could build up a hot plasma with I-p = 205 kA, n(e0) - 1.2 x 10(19) m(-3), T-e0 = 2 keV, a = 1 m and R-0 = 5.1 m.