The flexibility in respect of design and manufacturing freedom that additive manufacturing (AM) offer are key driving factors for many industrial scctors. For example, designing and manufacturing unique internal conformal cooling/heating channels with enhanced functionalities for various applications like tools and heat cxchangcrs. However, for the majority of the metal AM-processes in the as-build condition, AM is associated with high surface roughness, which has a measurable impact e.g on the heat transfer and flow properties. Hence, proper characterization of the fluid flow and heat transfer is vital to understand how the AM surfaces should be optimized for maximum output. The current study considers the cffcct of surface roughness and channels dimensions on the pressure drop and heat transfer. An experimental investigation was made of cooling channels produced by Powdcr-Bcd-Fusion using Lascr-Bcam-Mclting (PBF-LBM) additive manufacturing technique. Cooling channels with as-build surfaces was compared to post-processed cooling channels such as extrude honing and drilled channels, respectively. Results showed the lowest pressure drop for extrude honed channels compare to drilled and as-build channels, while heat transfer showed the same trend for as-build and extrude honed channels. The complexity of surface topography of as-build channels need to be described by parameters suitable for the detection of fluid interaction. Combination of different parameters remains to be investigated.