Highly cited papers are among the most commonly used indicators for measuring scientific excellence. The primary purpose of this study is to determine characteristics of highly cited papers authored or co-authored by Croatian researchers and to identify patterns of their national and cross-national collaboration. The Clarivate Analytics Web of Science Core Collection was used for collecting data. Data were filtered for the highly cited papers published in the 2008-2018 period. Half of 428 identified highly cited papers were published in only 18 journals. The distribution across subject areas showed a strong domination of the fields of physics and clinical medicine. The median number of authors per average paper was 30,5, while the same value in the case of Croatian authors was 2. Only 4% of the analysed papers were authored by Croatian researchers only. The national inter-institutional collaboration was marginal and mainly visible through joined collaboration with foreign institutions. European institutions are most frequently found among the authors’ addresses. For a small country on the scientific periphery, international cooperation is a prerequisite not only for the publication of highly cited papers but also for acquiring additional research experience in mainstream scientific teams.