The use of UV/EB cured materials as barriers against moisture vapor and/or oxygen gas has long been discussed. Depending on the final requirements and thickness of application, UV/EB materials can be successfully used for this application. Unlike some polymer chemistries and films, UV/EB cured polymers cannot be classified together in terms of barrier performance. Backbone chemistry, molecular weight, functionality, concentration of monomers or oligomers, hydrophobic/hydrophilic balance, density, cure conditions, and the presence of additives or fillers all play a vital role in predicting barrier performance. These variables are explored as performance predictors and compared with real barrier testing results.