By combining in-situ X-ray diffraction and atomic force microscopy, we investigate the structure and morphology of organic heterostructures formed by deposition of pentacene onto fluorinated copper-phthalocyanine (F16CuPc) films grown with two different molecular orientations. Well ordered pentacene films grow upon deposition on top of standing-up F16CuPc molecules (s-structure) and finally form homogeneous films. When pentacene is deposited on lying-down F16CuPc (l-structure), laterally small and high crystallites form. The pentacene preserves the same thin-film structure and excellent alignment along the surface normal in either case, with mosaicities of only 0.015 +/- 0.001 degrees. We demonstrate in this work how thin organic buffer layers can be employed to tailor the growth of ordered organic heterostructures. (C) 2008 Elsevier B.V. All rights reserved.