Electroexcitations of the dominantly T = 1 particle–hole states of 12C are studied in the framework of the harmonic oscillator shell model. All possible T = 1 single-particle–hole states of all allowed angular momenta are considered in a basis including single-particle states up to the 1f-2p shell. The Hamiltonian is diagonalized in this space in the presence of the modified surface delta interaction. Correlation in the ground state wavefunctions by mixing more than one configuration is considered and shows a major contribution that leads to enhance the calculations of the form factors. A comparison with the experiment shows that this model is able to fit the location of states and a simple scaling of the results give a good fit to the experimental form factors.