The massspectra of 3-aryl-3-hydroxyl-2,2,4,4-tetramethylcyclobutanones and their related compounds were studied. The arylcyclobutanones and their ketal forms demonstrate similar fragmentation patterns but with different observed common peaks, i.e., [M-70]+ and 114 amu, as the base peaks for compounds arylcyclobutanones and their ketal forms, respectively. 1-Aryl-2,2,4-trimethyl-1,3-pentadiones, obtained