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Nitride laser diodes (LDs), as compared with arsenide ones, are known to exhibit poor thermal properties, mostly because of a very intense heat generation within their volumes. Therefore, to enable their useful operation, they should be designed in a way enhancing efficiency of heat-flux extraction from their volumes. In the present paper, the finite-element approach has been used to compare heat-flux spreading mechanism in continuous-wave room-temperature threshold operated nitride laser diodes with four different mounting schemes. For the standard laser width of 300 μm, the maximal active-region temperature increase over the RT ranges from 33.3 K (for the best two-sided heat LD mounting with the diamond heat spreader on the p-side) to 50.0 K (for the n-side LD mounting). As expected, laser diodes attached to their heat sinks on their p-side exhibit much more efficient heat-flux extraction than those attached on their n-type substrate. Even more efficient extraction takes place for the two-sided laser mounting. Besides, an application of the diamond heat spreader considerably enhances the above efficiency disregarding the place of its application. Further improvements may be expected in new optimised nitride laser devices designed in a way enhancing both heat-flux flow through areas of high-thermal-conductivity materials (diamond, copper, but also binary nitride compounds) and a reduction of heat-flux paths through layers of low-thermal-conductivity ternary and quaternary nitride compounds.