A large body of empirical work has established the significance of cash flow in explaining investment dynamics. This finding is further taken as evidence of capital market imperfections. We show, using a perfect capital markets model, that time-to-build for capital projects creates an investment cash flow sensitivity as found in empirical studies that may not be indicative of capital market frictions. The result is due to mis-specification present in empirical investment-q equations under time-to-build investment. In addition, time aggregation error can give rise to cash flow effects independently of the time-to-build effect. Importantly, both errors arise independently of potential measurement error in q. We provide implications and recommendations for empirical work.JEL classification: D21; E22; E32; G31.