PCD composite constructions comprise a diamond body bonded to a substrate. The diamond body comprises a thermally stable diamond bonded region that is made up of a single phase of diamond crystals bonded together. The diamond body includes a PCD region bonded to the thermally stable region and that comprises bonded together diamond crystals and interstitial regions interposed between the diamond crystals. The PCD composite is prepared by combining a first volume of PCD with a second volume of diamond crystal-containing material consisting essentially of a single phase of bonded together diamond crystals. A substrate is positioned adjacent to or joined to the first volume. The first and second volumes are subjected to high pressure/high temperature process conditions, during process the first and second volumes form a diamond bonded body that is attached to the substrate, and the second volume forms the thermally stable diamond bonded region.