Abstract While (1-and 2-cycloheptatrienyl) phenylcarbonium ions undergo electrocyclizations through the cycloheptatriene forms giving dihydrobenz [a] azulenes,(3- cycloheptatrieny])-diphenylcarbonium ion does through the norcaradiene form.(7- Cycloheptatrienyl) diphenyl-carbnium ion undergoes a rearrangement. A possible rationalization is discussed.