Children with ADHD show deficits in processing speed (PS), as well as aberrant neural oscillations, including both periodic (oscillatory) and aperiodic (1/f-like) activity, reflecting the pattern of power across frequencies. Both components were suggested as underlying neural mechanisms of cognitive dysfunctions in ADHD. Here, we examined differences in PS and resting-state (RS)-EEG neural oscillations and their associations between 6–12-year-old children with (N=33) and without (N=33) ADHD. Spectral analyses of the RS-EEG signal using FFT revealed increased power in fronto-central theta and beta oscillations for the ADHD group, but no differences in the theta/beta ratio. Using parameterization method, we found higher aperiodic exponent, which has been suggested to reflect lower neuronal excitation-inhibition, in the ADHD group. While FFT-based theta power correlated with clinical symptoms for the ADHD group only, the aperiodic exponent was negatively correlated with PS across the entire sample. Finally, the aperiodic exponent was correlated with FFT-based beta power. These results highlight the different and complementary contribution of periodic and aperiodic components of the neural spectrum as metrics for evaluation of PS in ADHD. Future studies should further clarify the roles of periodic and aperiodic components in additional cognitive functions and in relation to clinical status.