Mass tour operators, host holiday destinations and tourists have as common interest the preservation of attractive natural surroundings, positive encounters between visitors and the host community as well as welfare for business and society. Sustainable tourism has been presented the past two decades as new concept idea for arranging tourism services and products. The Tour Operators Initiative for Sustainable Tourism Development supported tour operators in the process toward better sustainability in business operations by sharing knowledge and good practices in a pilot project from 2000 to 2014. Mass tour operators’ sustainable operations reflected in their site communications are inter-dependent with both the demand side and destinations host suppliers. Dutch and Finnish tourists are introduced with their attitudes and interests in tourism for a better understanding of the communication content of mass tour operators in Finland and the Netherlands. Coastal Mediterranean Europe destinations in Spain and Greece are presented with the current situation and sustainability developments as Planet, People and Prosperity communications are only possible with a certain degree of environmental, social and economic practices at the destination. The thesis studied the integration of sustainability at the Planet (environment), People (socio-cultural) and Prosperity (economic) levels in communications by Finnish and Dutch mass tour operators. The site customer communications of the Dutch mass tour operators TUI (ARKE), Neckermann Reizen and Sudtours Vliegvakanties and Finnish tour operators Finnmatkat, Tjareborg and Aurinkomatkat are explored in a comparative research. The purpose was to study the emphasis balance of the 3P concept in Finland and the Netherlands. The study focused on site communications in customer relations. The communicative elements informing, coaching and sharing as well as sales text have been used in the research for a more holistic insight. Dutch and Finnish tour operators showed equal good ...