The chemical activation of anthracites with hydroxides has been shown to be of interest for the production of activated carbons with a highly microporous structure. In a previous paper, attention was placed on the reactions occurring during the chemical activation of an anthracite by NaOH and KOH. In the present work, the process of chemical activation by hydroxides has been extended to different coal precursors to confirm that such a chemical activation process starts through a solid–solid reaction and continues as a solid–liquid reaction. In such a solid reaction, the reactivity of the solid (precursor) should be a key parameter. The importance of the carbon reactivity on its reaction with hydroxides has been confirmed: the lowest rank coal reacts much easily and has a much lower temperature for the beginning of reaction than the highest rank coal.