A growing interest has emerged in the role that autobiographical memory retrieval plays in simulation of future events. Cognitive explorations in this domain have generally relied on cue word paradigms with instructions to develop specific (relating to one particular day) memories or future events. However, the usefulness of this paradigm has been questioned with respect to its ability to assess habitual patterns of retrieval within autobiographical memory. The current study investigated similarities and differences in how participants spontaneously remember the past and imagine the future when the specificity constraints inherent in the cue word task are removed. A total of 93 undergraduate students completed two sentence-completion tasks, probing for past and future events. A number of differences emerged between past and future thought; in particular, they were less specific when simulating future events compared with past events. This reduction in specificity was the result of participants producing more future thoughts relating to extended lifetime periods and semantic associates. The findings are discussed in relation to the underlying cognitive processes involved in autobiographical memory retrieval and future event simulation.