The role of hydrated electrons in sonochemiluminescence (SCL) arising from the single- and multibubble sonolysis of aqueous solutions of $${\text{Ru(bpy)}}_{{\text{3}}}^{{{\text{2 + }}}}$$ and $${\text{Ru(bpy)}}_{{\text{3}}}^{{{\text{3 + }}}}$$ is revealed. Possible chemiluminescent reactions between ruthenium ions and the products of water sonolysis are considered. A conclusion is drawn concerning the previously unknown formation of eaq upon the single-bubble sonolysis of water and the absence of this product upon multibubble sonolysis.