Purpose: The purpose of this paper is to assess costs in the National and University Library of Croatia for processing Croatian web resources and the maintenance and development of the service, and to analyse the present organisation and workflow of their processing, and to propose improvements. Design/methodology/approach: The assessment period was two months, during which the members of staff involved minutely monitored their tasks. The results were compared to the same exercise reported by the National Library of Australia and processing costs of cataloguing Croatian print publications. Findings: The bottom-up analysis of processing web resources shows that a balanced description of tasks and their distribution over staff members was established, and that the present workflow meets the requirements of efficient processing of web resources. As a general finding, approximately the same time was spent on archiving new items, as on the control and maintenance of the already archived ones due to the change of web resource properties, URL instability and the changes of technology. The comparative analysis showed: less time is spent on identification and selection and publishers' contacts on the part of the Croatian National Library compared to the Australian one; almost twice as much time was spent on gathering, quality assurance, and archiving instances in the Australian case than in the Croatian one; practically the same time was spent on cataloguing in both cases; and compared to cataloguing of print publications, significantly less time was spent on the print ones. Originality/value: The paper is one of the two published articles on the in depth analysis of the workflow and processing costs of managing and selectively archiving legal deposit copies of web resources in a national library. Its potential value is in drawing attention of library managers of those institutions that deal with selective web archiving to assess costs and services in view of the legal obligations of libraries for preserving national cultural web heritage and meeting present and future users' needs. (Contains 10 figures and 8 tables.)