The impact of the scientific output produced by different nations in different fields varies extensively. Inthis article, we apply bibliometric and econometric analysis to study how citation impact varies acrosscountries. This paper differs from previous research in that a cross-section model is put forward to accountfor such variation. A special focus is given to the Global South, as countries in this group have beenconverging with the Global North recently. We find that previous citation impact, level of internationalcollaboration and total publications in a specific scientific field are important determinants of citationimpact among all nations. However, specialization in particular scientific fields seems significantly moreimportant in the Global South than in the Global North. These findings imply that most lower- andmiddle-income countries would better concentrate their resources in generating higher critical massesin specific fields, in addition to pursuing long-lasting international collaboration partnerships, as theseactions may lead to higher impact research.