AbstractAlthough Jakobson’s (1959) seminal classification of translation into three kinds: interlingual, intralingual and intersemiotic has been widely accepted in Translation Studies, so far most research interest has focused on interlingual translation, defined as “translation proper”. Intralingual translation, more often understood as rewording, paraphrasing or reformulation within the same language, is a less prototypical kind of translation, yet we believe that the underlying mental operations needed to perform both tasks include similar processing stages. Bearing in mind the lack of research comparing inter-and intralingual translation we designed the ParaTrans project in which we investigate how translators make decisions in both tasks. In this article we present the results of a comparative analysis of processing effort and cognitive rhythm demonstrated by professional translators who were asked to translate and paraphrase similar texts. Having collected three streams of translation process data with such tools as key-logging, eye-tracking and screen-capture software, we are able to draw some tentative conclusions concerning the similarities and differences between language processing for interlingual translation and intralingual paraphrasing. The results confirm a higher processing effort in interlingual translation most likely due to the need to switch between languages.