Reaction of NH-pyrazoles with 1-bromoadamantane in a high pressure stainless steel autoclave gives regioselectively 1-(1-adamantyl)- or 4-(1-adamantyl)pyrazoles depending on the temperature. A series of cross-experiments allows to establish the mechanism of this reaction. The molecular structure of the most simple derivative, 4-(1-adamantyl) pyrazole (3a), has been determined. Intermolecular N-H ... N hydrogen bonds hold the four independent molecules together in a helix system parallel to the c axis. The crystal is built up of two centrosymmetrically related helices.