this study attempted to explore if teaching english collocations through two different modes of awareness-raising and input flooding has any possible differential effect on immediate retention as well as retention in a delayed assessment. it also compared the possible differential effect of teaching english collocations implicitly and explicitly on actively using the items in writing. moreover, this research tried to out if presenting english collocations through input flooding and awareness-raising has differential effects for lexical and grammatical collocation in both short and longer terms. as the final and fourth question, this study investigated the possible differential effect of the two types of collocations in the two modes of instruction on activation of these items in writing. the data were gathered from 60 homogenous participants who went through input flooding and awareness-raising instruction modes on the two types of collocation. multiple-choice items were produced and used to assess immediate and longer term retention of the items targeted in the treatment. to measure the active use of collocation items, fill-in-the- blank format was utilized. a series of t-tests, anovas, post-hoc tests, and tests to estimate normal distribution were used to analyze the data. the findings shed light on the difference between the two modalities while highlighting the strengths and weaknesses of each. generally, the main findings pointed to the significant superiority of awareness-raising mode of instruction over input flooding. however, part of this advantage seemed to disappear in the delayed test.