The present invention provides novel compositions, kits and methods employing RNA 5′ polyphosphatases, RNA 5′ monophosphatases, capping enzymes, decapping enzymes, nucleic acid pyrophosphatases and RNA ligases, as well as other enzymes, for selective 5′ ligation tagging of desired classes of RNA molecules that differ with respect to particular chemical moieties on their 5′ ends. The 5′ tagged RNA molecules can be used for synthesis of tagged first-stand cDNA, double-stranded cDNA, and sense or antisense RNA for a variety of uses.