The greatest change in VB6 and VB.NET is of runtime environment. VB6 used the VB-Runtime while VB.NET uses the .Net Common Language Runtime (.Net CLR). The CLR is much better designed and implemented than VB-Runtime. The CLR uses better code translation through Just in Time compiler while VB-Runtime interprets the code. The CLR Garbage Collector is also more efficient than VB6 one as it may detect cyclic references too.