A quantum theory developed earlier is used to study the cyclotron-resonance linewidth for the electron scattering via the acoustic phonon, the ionized-impurity, and the piezoelectric scattering mechanisms. For the electron-acoustic-phonon scattering, the linewidth is found to increase linearly with the magnetic field, while the peak-value decreases with the increasing magnetic field. For the electron-ionized impurity scattering, the linewidth decreases with magnetic field, while the peak-value increases. The linewidth and the peak-value are independent of the magnetic field in the case of piezoelectric scattering. Under the combined effect of all three scattering mechanisms, a minimum of the linewidth as a function of the magnetic field is predicted. The critical magnetic field for which the linewidth is minimum and the minimum value of the linewidth are found to vary as the square-root of the impurity concentration. Wherever possible, comparison is made with the existing experimental data.