Tourist industry for Greece, as well as for the countries of Southern Europe constitutes a significant economic factor, attracting a considerable amount of investments. In addition, a significant portion of human resources is employed or self-employed in tourist activities. The world conditions, the globalisation of economies, environmental and climatic changes, the creation of new markets and the turning to new aspects of tourism changes the situation in this sector, providing new dynamics and opportunities for further development.

Operational research contributes to the study of problems, the identification of solutions and activities, as well as to the depiction of directions in all the aspects of tourism industry, such as hotel management, coastal transport, quality of services and others. The development on tourism was the main subject of the 20th Conference of the Hellenic Operational Research Society, which took place in the island of Spetses and attracted more than 120 researchers. Selected research works from this conference are published in this special issue covering the subject of the conference, as well as other aspects of main streams in operational research. Six papers were selected from a set of 26 submissions.

In the first paper, Vazakidis and Karagiannis focus on the utilization of activity based management approaches to the hotels, incorporating information technology in order to face problems arising from the need to manage services.

The second paper by Stiakakis and Georgiadis deals with the crucial drives for the design and implementation of an e-business strategy in tourism analyzing three main issues, namely (a) customer relation management, (b) supply chain management, and (c) information and communication technology products.

In the next paper, Petropoulou, Retalis, and Vassilikopoulou present and analyse an approach for the evaluation of students’ performance in e-learning environments through a multi-rubric (criteria) approach.

The paper by Psaromiligkos, Orfanoidou, Kytagias and Zafeiri, is also focused on e-learning. The authors present proposed the use of data mining techniques in order to analyse and explain learners attitudes in e-learning systems function on the web.

In the fifth paper Gkoulalas-Divanis and Verykios present an algorithm for the improvement of the anonymity capabilities in location based services networks.

The special issue closes with the paper of Koutsantonis and Panayiotopoulos, who present a new generation of knowledge management systems that support personalized knowledge retrieval utilising innovative architecture of enriched knowledge objects for knowledge representation.

I would like to sincerely thank all authors, reviewers and participants of the conference for their fruitful contribution.