To use more effectively the limited resources available for conservation there is an urgent need to identify which conservation approaches are most likely to succeed. However, measuring conservation success is often difficult, as it is achieved outside the project time frame. Measures of implementation are often reported to donors to demonstrate achievement but it is unclear whether they really predict conservation success. We applied a conceptual framework and score-card developed by the Cambridge Conservation Forum (CCF) to a sample of 60 conservation activities to determine the predictive power of implementation measures versus measures of key outcomes (later steps in the models defined in the CCF tools). We show that assessing key outcomes is often more difficult than quantifying the degree of implementation of a project but that, while implementation is a poor predictor of success, key outcomes provide a feasible and much more reliable proxy for whether a project will deliver real conservation benefits. The CCF framework and evaluation tool provide a powerful basis for synthesizing past experience and, with wider application, will help to identify factors that affect the success of conservation activities.