Investment frictions reduce, delay or protract investment expenditure that is necessary for firms to capture growth opportunities. Using a capital adjustment costs framework, this article estimates the gap between China's actual and frictionless aggregate output. It applies the method of simulated moments to a fully structural investment model on a panel of Chinese firms and takes into account potential unobserved heterogeneities and measurement error in the data. The estimated capital adjustment costs imply that if Chinese firms had faced a lower level of adjustment costs such as in the US, China's aggregate output would be 25% higher.