Abstract. In this note, we study a new Finslerian quantityĈ defined by the Riemannian curvature. We prove that the new Finslerian quantity is a non-Riemannian quantity for a Finsler manifold with dimension n = 3. Then we study Finsler metrics of scalar curvature. We find that theĈ-curvature is closely related to the flag curvature and the H-curvature. We show thatĈ-curvature gives, a measure of the failure of a Finsler metric to be of weakly isotropic flag curvature. We also give a simple proof of the Najafi-Shen-Tayebi' theorem.1991 Mathematics Subject Classification. 58E20. Recently, a great progress has been made in studying Finsler metrics of weakly isotropic flag curvature. These Finsler metrics are of scalar curvature whose flag curvature is in a special form K = θ/F + σ where θ is a 1-form and σ is a scalar function on M. Finsler metrics of weakly isotropic flag curvature not only include Finsler metrics of constant flag curvature, but also include Finsler metrics of (almost) isotropic S-curvature and of scalar flag curvature [4, 6, 13]. Cheng and Shen have