Flexible structures usually possess vibration modes with close, but not exactly repeated, natural frequencies. Quantifying the controllability and observability of such modes is a nontrivial. task; this contrasts with the case of modes that are either exactly repeated or widely separated. This paper derives expressions for the degrees of controllability and observability of near-repeated modes by examining the closed-form Grammians of flexible structures. The results obtained quantify the role of damping and frequency separation in controllability and observability.