We study the patch dynamics on the whole plane and on the half-plane for a family of active scalars called modified SQG equations. These involve a parameter α which appears in the power of the kernel in their Biot-Savart laws and describes the degree of regularity of the equation. The values α = 0 and α = 1 2 correspond to the 2D Euler and SQG equations, respectively. We establish here local-in-time regularity for these models, for all α ∈ (0, 1 2 ) on the whole plane and for all small α > 0 on the half-plane. We use the latter result in [16], where we show existence of regular initial data on the half-plane which lead to a finite time singularity.