Selective laser melting (SLM) process is a promising additive manufacturing technique for the fabrication of 3D metallic components with complex geometries. When applied to a porous structure made of a low-alloyed copper, the results show a good producibility and malleability for structures made of CuNi2SiCr. On the other hand, powder metallurgy proposes spark plasma sintering (SPS) process to introduce diamond particles (resin-bonded micron-size and crystalline with 50 % coating) into a 3D-built copper structure to achieve fast and highly densified fabrication. The present work aims to achieve better positioning, consolidation and densification of the diamond particles at the desired location of the structure, which includes both the lattice and the bulk. This paper studies an additively manufactured diamond-reinforced copper structure developed for fabricating heatsinks by SLM and SPS. These metal-diamond hybrid composites can potentially be used for electro-thermal applications, refractory composites or bio/tribological applications. The demonstrated privileges include i) AM techniques using SLM with low laser power, ii) larger layer thicknesses with higher productivity and iii) rapid fabrication of porous structures with successively applying plasma sintering to fill them with hard materials like diamond particles.