The 1, 3-dipolar cycloaddition of arylazides with 1, 2-dihydro-isoquino line derivatives leads to new triazolinic adducts. The thermolysis of these latters followed to a hydrolysis conducts to 1, 4-dihydroisoquinolin-3 (2H)-oes. The structure of the adducts and other products are assigned. The regio and diastereospecificity of the cycloaddition reaction are discussed on the basis of 1H NMR data.