Latest trends in optical lithography will dramatically change the way we need to look at defect printability and the impact that defects have on the performance of our devices. The prediction is, that linewidth variations will have the most severe impact, causing devices to perform under specification, or at least costing the manufacturers substantial photo limited yield by having to bin die in lower speed performance bins. A mask error enhancement factor may actually make defect print more severe in certain pattern, context, and linewidth variations across the pate will cause severe problems in the device manufacturing process to maintain ACLV at an acceptable level. Having to use RET technologies, such as OPC and PSM, may actually aggravate the printability problems. In this study, a special reticle design was used to investigate defect sizes, location and permutation, to evaluate: (i) defect sensitivity and capture in an advanced reticle inspection system, (ii) printability prediction using a sophisticated wafer image simulation software package, (iii) printability of 'traditional' vs. hidden linewidth error defects, (iv) the true CD impact of a given defect on LW performance using an advanced CD-SEM.