In the early 19th century, posters were used to advertise the products, information and events associated with a company. From the mid 19th century, companies started using posters to highlight their brand, and thereby focused more effort on how they presented their image to the public. As technology progressed, more emphasis was put on simplicity, metaphor and the visual impact of colors in poster designs, rather than on mere text-based messages. Lithography, which was invented in the mid 19th century after the industrial revolution, contributed a great deal to the rapid development of poster design. After typography was invented by Johannes Gutenberg, and in view of the human thirst for knowledge, the importance of and need for information began to rise. That led to mass production of posters, which have become the most common printing medium for publishing and advertising. In the 20th century, a new trend in poster design began to emerge. The focus turned to the holistic visual impact of posters, leaving behind the approach of illustration through words. Accordingly, this study employs the semiotic approach in analyzing the visual quality of posters, which represents the social and cultural trend of the 20th century. In that regard, to analyze the features of visual elements, which fully formed the poster culture, this study examines the posters displayed at the "World`s Posters for a Hundred Years in the 20th Century" exhibition in 2002, organized by Doosung Paper Co. Based on that, this study explores semiotic elements as visual expressions to convey the meaning of posters in view of their relevant social background in various countries during different years between 1900 and 2000 when there was dramatic growth in poster design. Understanding the process of changes that occurred during that period would contribute to achieving a clear picture of history of the 20th century`s poster design culture.