When do NPV and IRR give different conclusion regarding accepting a project?

NPV (Net Present Value) and IRR (Internal Rate of Return) can yield different conclusions when evaluating projects with non-conventional cash flows, such as multiple sign changes in cash flows, or when comparing mutually exclusive projects with different scales or time horizons. NPV is generally preferred for its absolute value indication of profitability, while IRR can be misleading in such cases, potentially suggesting a higher return on a less favorable project. Additionally, if the cost of capital is higher than the IRR, a project may still be rejected based on NPV, which reflects the actual value added.