Aims and Objectives of the paper: Sustainable development initiatives encourage more greenery in urban space. Visual and psychological impacts caused by such changes to urban form could result in cognitive spatial representations that are different from their objective equivalents. Subsequent utilization of such misrepresentations could have undesired results in terms of usage of space or even human frustrations. In the process of understanding such possible misrepresentations, our work was aimed to clarify how the introduction of vegetation could affect cognitive distance, one important aspect of spatial representation. We further investigated on the sensitivity of cognitive distance to the differentiation four vegetation design parameters.Context and background literature: Previous researchers have identified vegetation as a probable contributor to good spatial representation. Human preference and cognitive systems are proved to be affected by presence and design of vegetation. Feature accumulation theory and Route segmentation theory explains how environmental features cause differences in cognitive distances. Considering street trees as the environmental feature we try to establish how the variation of this feature could affect cognitive distance.Method of inquiry or argument: By varying the vegetation design parameters growth stage, spacing, tree species and canopy condition 36 vegetation designs were obtained. The cognitive distance judgments of the subjects` using each of 36 photo-simulated streets both in vegetated and non-vegetated condition were evaluated and analyzed. Findings and conclusions: While proving the effect of vegetation on cognitive distance, results showed that subjects overestimated the distances in the vegetated settings in comparison to the non-vegetated settings. The spacing of trees was found to be affective on cognitive distance judgment. Applicability to the field and work to be done next: Longer cognitive distance representation such as due to the introduction of vegetation could result in unused spaces. Realization about the mismatch between objective values and subjective judgments could lead to user frustrations. Designers and planners should consider how the presence of vegetation could affect the human cognitive representations and treat possible misunderstandings such as through improved information. In the next stage other aspects of spatial cognitive representations would be investigated in a virtually simulated environment allowing navigation.