A steerable instrument has an actuator at a proximal side and a bendable zone at a distal side. The actuator controls bending of the flexible zone by means of one or more longitudinal elements. The instrument has a first cylindrical element, a second cylindrical element and a third cylindrical element. The second cylindrical element has a zone with a longitudinal element portion with a first height in a radial direction of the instrument. Radial spacers are located at mutual sides of the longitudinal element portion, which have, at least locally, a second height in the radial direction larger than the first height.