Currently there is a general uncertainty about what makes collocations (i.e., fixed word combinations with specific, not easily interpreted relations between their components) hard for ESL learners to master, and about how to improve collocation recognition and learning process. This study explored and designed a comparative classification of external factors that affect adult English as L1 and L2 speakers' recognition of false (non-native-like) collocations. At Stage 1, the reading-comprehension test and interview were administered to 5 participants: emergent bilinguals (another language/English), an advanced bilingual (Russian/ English), and a monolingual speaker of English. The results provided insights into the strategies and criteria participants employed to identify false collocations. At Stage 2, more than 90 speakers of English as L1 and L2 took a reading-comprehension test and posttest survey that gathered information on the differences and similarities in the participants' collocation recognition. The results suggested that certain factors positively correlated with recognition of false collocations: English as a predominant language of communication, the length of residence, vocabulary-learning strategies, and the focus of attention on sentence structure and the form and meaning of word combinations. The implications concern potential focus areas for pedagogical intervention in the ESL classroom.