The invention relates to a steerable instrument (10) for endoscopic and/or invasive type of applications, such as in surgery. The instrument comprises an elongated tubular body (18) having a proximal end part(11) comprising at least a first actuation flexible zone (14, 15) having a first diameter and a distal end part (13) having at least a first distal flexible zone (16, 17) having a second diameter that is different from the first diameter. The elongated tubular body further comprises a cylindrical diameter adaptation section (164) that is arranged to connect the proximal end part (11) to the distal end part (13) such that a flexion in a radial direction relative to a longitudinal center axis of the longitudinal tubular body of for example the at least first actuation flexible zone (14, 15) results in one of an amplified and an attenuated flexion in a radial direction relative to a longitudinal center axis of the longitudinal tubular body of the at least first distal flexible zone (16, 17). If the first diameter is larger than the second diameter, the flexion of the at least first distal flexible zone is amplified. If the first diameter is smaller than the second diameter, the flexion of the distal flexible zone is attenuated.Linvention se rapporte à un instrument orientable (10) pour un type dapplications endoscopique et/ou invasif tel quen chirurgie. Linstrument comprend un corps tubulaire allongé (18) ayant une partie dextrémité proximale (11) comprenant au moins une première zone flexible dactionnement (14, 15) ayant un premier diamètre et une partie dextrémité distale (13) ayant au moins une première zone flexible distale (16, 17) ayant un second diamètre qui est différent du premier diamètre. Le corps tubulaire allongé comprend en outre une section dadaptation de diamètre cylindrique (164) qui est conçue pour raccorder la partie dextrémité proximale (11) à la partie dextrémité distale (13) de telle sorte quune flexion dans une direction radiale par rapport à
