This study investigated the spatial summation properties of excitatory and inhibitory neuron subtypes in the mouse visual cortex. Two-photon calcium imaging was used to measure the size tuning curves of pyramidal (Pyr), somatostatin (SOM), and parvalbumin (PV) neurons. The results showed that Pyr neurons preferred small stimulus sizes and exhibited strong suppression for larger sizes, indicating their role in surround suppression. In contrast, SOM neurons preferred large stimulus sizes and did not show suppression, suggesting they inhibit Pyr neuron responses. PV neurons had intermediate size tuning preferences and strong suppression, but their exact role requires further study. These findings provide insight into how different cortical neuron types process visual information.