Determining the optimal policy response to a species invasion is a multidimensional problem. The choice between eradication or containment has social, environmental, political and economic dimensions. Often, economic evaluation is used as a basis to underpin policy decisions. However, under certain conditions economic evaluation criteria may provide conflicting results. Deterministic factors, such as rate of spread, degree of damage and the time until detection, are derived for identifying when caution must be taken with the results of economic evaluation criteria. The conditions under which conflicting results may be obtained between NPV and BCR are identified and linked to policy implications.