Gap waveguide technology represents an emerging and interesting solution for the development of circuits and components operating in the millimeter-wave and sub-millimeter-wave region. In this new guiding structure the energy is transmitted through the air gap existing between two parallel metal plates with a HIS boundary condition to assure energy confinement. These conditions are implemented by means of a multiplicity of conducting nails periodically distributed on both sides of the guiding media. This paper resents a new of the Gap Waveguide concept using low temperature co-fired ceramic technology (LTCC) in sub-millimeterwave band. Compared to substrate integrated waveguide (SIW) technology, the first interest is the minimization of dielectric losses due to the propagation in air. Furthermore, it is shown that the technological constraints are less severe than for the conception of SIW waveguide (diameter and periodicity of vias). The concept is illustrated with a gap waveguide example working at around 170 GHz.