The needles and twigs of black spruce—Picea mariana(Mill.) B.S.P.—were analyzed for the composition of their essential oil after having been submitted to hydrodistillation. The composition of the essential oil is significantly influenced by the preparation of the samples: whether prepared as two-cm pieces or macerated in a blender. Depending upon the preparation of the samples, the major components are, respectively: α-pinene (7.4 and 13.5%), camphene (14 and 21.2%) and bornyl acetate (41.8 and 29.6%). Sixteen constituents are reported for the first time.