Purpose: Bronchial stents are devices to keep an airway open when it has been obstruct by extrinsic or intrinsic tumor compression. Such device may be in use in a patient undergoing photodynamic therapy (PDT). The magnitude of the light attenuation by commercially available stents is unknown. To study the attenuation properties of four different kinds of commercially available bronchial stents that may be used in PDT. Method and Materials: The stents were a Nitinol mesh, a polyester mesh, a solid silicone and an opaque solid silicone, all manufactured by Boston Scientific. These stents were cut longitudinally so that each could be sandwiched in a 10 × 10 PMMA holder. For each measurement, the holder with and without the stent was positioned between a PDT laser beams (630 nm, 100 mW) and a laser power/energy monitor. The attenuation was obtained by the ratio of the light intensity that reaches the detector after traverse the PMMA with and without stent, respectively. Results: The Nitinol stent attenuated the light beam by 30.7%, the polyester stent by 51.1%, the transparent silicone stent by 7.83% and the opaque silicone stent by 80.8%. Conclusion: Bronchial stents can great attenuate the light in PDT, so that attenuation of a particular kind of stent should be evaluated, taking into account also treatment time and light intensity, before its use in a patient undergoing PDT.