This thesis aims to provide some coverage of the increasingly important marketing area of Electronic Word of Mouth from a different angle to that provided thus far in the marketing literature. The primary aim of this research is to provide an understanding of the nature of product and service oriented Electronic Word of Mouth messages conveyed via the social media platform Instagram. The already noted power of Word of Mouth as a communication form coupled with the unique properties of Instagram as a communication platform provide a highly useful basis for contribution to the marketing domain. Unlike some previous Word of Mouth oriented studies, this research chose to employ a content analysis methodology in order to examine the Instagram based Word of Mouth communication. This approach enabled the communication itself to be placed as the focus of the research whilst also enabling that communication to be examined in its native and unadulterated state. To implement the content analysis, a total of one thousand Instagram posts featuring the four product and service based categories of Cars, Clothes, Restaurants and Holidays were sampled. The content from these posts was then analysed using a coding scheme comprising of the four content themes of Emotive Content, Company Linking, Commercial Intent Content and Recommendation Content. The variance in these four content themes between the four product and service based categories was then calculated as per the research hypotheses. Additionally, the frequencies for the different content measurement units for each of the content themes was recorded along with the different forms of image used in the posts sampled from each of the four product and service categories. Ultimately, many of the variance results failed to support the research hypotheses, however the presence of other statistically significant results and in some cases the absence of significant results did provide some useful alternative findings. In the sole case that the research hypothesis was supported, the results indicated that Instagram posts featuring the service categories of Restaurants and Holidays featured a higher level of Recommendation Content than those featuring Cars and Clothing. These results, coupled with the frequency results for both the image types and content measurement units enabled the three broader research themes of the prominence of emotion, relative focus on self and lack of commercialisation to be derived. The implications of the study in both theoretical and practical terms, along with the limitations of the study and subsequent suggestions for future research are also discussed.