Is ColdFusion 9 backward-compatible with previous releases of ColdFusion?
ColdFusion (MX 6.x, 7, and 8) applications should seamlessly migrate to ColdFusion 9. Most ColdFusion 5 applications can also be migrated easily to ColdFusion 9. For details on migrating from ColdFusion 5 or earlier to ColdFusion 9, visit the ColdFusion MX migration resources section of the ColdFusion Developer Center.