Understanding of the interaction between cellulose and various plastics is crucial for designing waste-to-energy processes. In this work, co-pyrolysis of polystyrene (PS) and cellulose was performed in a Py-GCXGC/MS system at 450-600 degrees C with ratios 70:30, 50:50, and 30:70. Polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET) were then added to the mixture with different ratios. It was found that co-pyrolysis of PS and cellulose promotes the formation of aromatic products with a large increase in the yield of ethylbenzene as compared to the calculated value from individual feedstock. This indicates interactions between cellulose and PS pyrolysis products. Observations from experiments including more than one type of plastics indicate that the interactions between different plastics are more pronounced than the interaction between plastics and cellulose.