Respiration occurs in the light and dark, but respiration in the light (RL) is the least understood and most poorly represented in models. This is because RL often happens spontaneously with carbon fixation during photosynthesis, making it challenging to measure. Furthermore, some evidence suggests that CO2 released during RL may be refixed in the cell when photosynthesis is high; which could lead to inaccurate estimations of RL. Nevertheless, the literature currently suggests that respiration is suppressed in the light. Our question was whether RL is truly light dependent or if it is an artifact of refixation.  Using a new measurement technique, we measured the 12CO2 efflux from a leaf (RL) in a 13CO2 environment with a tunable diode laser. We collected RL light response curves under ambient (440ppm), and high (1200 ppm) 13CO2 concentrations. Our hypothesis was that refixation of 12CO2 would be less likely to occur under extremely high 13CO2 concentrations, allowing us to measure the total 12CO2 emitted from the leaf. Thus, if there were no refixation in the leaf, the light responsive curves would all have the same RL as our control concentration (440ppm) at each light intensity. However, if refixation were occurring, then the high 13CO2  light response curves would disappear or be muted. We concluded from the subsequent light response curves that refixation was occurring in the tested leaves, but the magnitude of the process remained small. Additional research is needed to fully understand the response of RL to changes in CO2 concentration.