Emodin (6-methyl-1,3,8 trihydroxyanthraquinone) is considered as a potential candidate for photodynamic therapy for the treatment of cancer. A success in using of the molecule depends among other factors on the knowledge how fast it penetrates through the cell membrane and then diffuses inside the cell. A spatial distribution of emodin inside cancerous cells is also an important factor. The aim of this study is to investigate the diffusion of emodin in cancerous cells by means of a non invasive and sensitive technique: Surface Enhanced Raman scattering which permits us to study the evolution of the small amount of emodin inside single living cells. The experimental results were compared with a theoretical model that simulated the Brownian diffusion of particles. From this comparison and comparing with previous results in fluorescence spectroscopy we have found that: for a long time, emodin is accumulated in the cytoplasm in a region close to the membrane. The result is discussed in terms of emodin being stored in cell organelles located in the cytoplasm.